Build a killer gaming PC for $100

Turn old parts into a frugal fragging machine.

Man opening a trash can.
One person's garbage is another one's gateway to spending endless hours playing video games.Whitson Gordon.

Building your own computer from scratch allows you to craft the perfect rig for your needs, but if you’re on a super-strict budget, a shiny, new, custom-built PC isn’t always feasible.

So it’s a good thing you don’t need one of those to play games.

Sure, $400 or $500 might build you a decent budget machine, but if money is tighter than that, your best bet is to go with something used. You might get lucky and find a decently priced gaming computer on Craigslist, but you’ll get better bang for your buck going with something more common and less specialized: a decommissioned office PC.

That’s right—with a few choice upgrades, those Dell towers that litter office buildings ‘round the world can actually make decent gaming rigs. And your town is probably crawling with them, since schools and businesses often get rid of them in large batches.

Their loss is your gain—let’s bring one of those suckers back to life.

What you’ll get

Before you start hunting for hardware, you’ll need to set your expectations. Even with a few upgrades, a low-end PC such as the Dell Optiplex I found won’t be playing all the latest triple-A titles at high resolutions with beautiful, ray-traced graphics. It will, however, handle a lot of lower-requirement esports titles like Counter-Strike: Global Offensive, League of Legends, Fortnite, Overwatch, and Rocket League. Depending on the upgrades you make, higher-end games like Shadow of the Tomb Raider might be playable if you’re willing to turn the resolution down to 720p. (If you run into any trouble, though, YouTube channel LowSpecGamer has a lot of tricks for playing newer games below the minimum system requirements.)

Open PC tower
It doesn't look like much now, but with a little love, this baby will help you win hundreds of battles. Whitson Gordon

Of course, you’ll also be able to grab games from a couple years ago during a Steam sale and play them without much issue, for super cheap. And since “Gaming” doesn’t just mean playing the latest graphical behemoths on launch day, you can also dig further back to classic masterpieces on stores like GOG.com.

Finally, know that this PC probably won’t be a long-term investment, so consider it a stopgap until you can afford a more powerful build. After all, we’re talking about pretty old, well-used hardware, and you can only upgrade it so far before it makes more sense to build a new PC from scratch. It also may require a bit more maintenance, so be ready to tackle problems if they happen—and make sure you have a good backup solution handy for your data.

If all that sounds palatable, it’s time to start deal hunting.

Where to find your parts

You can find used computer parts all over the web, but the best deals are probably right in your neighborhood. I recommend pounding the pavement and finding your local electronics recycling centers, office liquidators, and thrift stores—give them a call or pay them a visit to see what kind of used PCs and PC parts they have. Alternatively, if you know people at local schools and businesses, ask them if their IT department is looking to offload any old gear.

Screenshot of Craiglist
It might go without saying, but you should always test the PC before handing over any money.Whitson Gordon

You’ll be able to find a lot of the components you’ll need this way, but not necessarily all of them. For anything you can’t find at an e-waste center, you’ll want to scour Craigslist, OfferUp, LetGo, and other similar apps. You can also try eBay, but the platform has a much larger audience, which means stuff tends to sell for its fair market price. But you’re scraping together a PC on the lowest budget possible, so market price is not what you want: you want a local seller who’s willing to negotiate a killer deal just to get it off their hands. (You can even try to find some parts for free, but I wouldn’t bank on that too hard—especially if you want stuff in decent working order.)

Buying local also allows you to test the equipment before you hand over your money. When negotiating the sale, ask the seller to have it plugged in and ready to try when you go to pick it up. That way you can see if it boots into Windows, run CrystalDiskInfo to see if the hard drive is still in good shape, and make sure it doesn’t reek of smoke (seriously—this is more common that you’d think). If the PC doesn’t have a hard drive—it’s common for companies to destroy them for security reasons before they dispose of their computers—see if it boots into the BIOS, or bring a flash drive with the Windows installer on it and see if it boots into that. If everything looks reliable, you can take it home and start working on your upgrades.

Online sales like eBay do offer buyer protection, though, which is handy if you get a defective component. Craigslist doesn’t usually have any recourse for that, so you’ll have to weigh your risk tolerance with your budget and go from there.

What to look for

As with any PC build, it helps to plan things out before you actually go shopping. (We’re assuming you already have a general idea of what goes into building a PC—if you don’t, you should definitely become acquainted with our PC building guide first.) Lay out your budget, figure out which parts will fit into it, then start your hunt. My goal was to build something for only $100 (because hey, I like a challenge), but I’ll lay out parts in a few different price ranges for those who have more to spend.

The tower

PC tower
You've basically saved this poor PC tower from endlessly running Excel. Whitson Gordon

There are a few different types of office-oriented PCs out there, but the Dell Optiplex is one of the more common and the one I’d recommend for this conversion. If you can find a Lenovo, HP, or Compaq machine with similar specs for a good price, you can use those too, but they’re a bit harder to come by. You’re looking for something that, ideally, has a second generation Intel Core i5 processor (in which the four-digit number after i5 starts with a 2) or newer processor—an i3 might get you by, but avoid Core 2 Quads and other lower-end CPUs if you can.

These office PCs also come in different forms. I recommend getting a larger “mini tower,” rather than one of the smaller, slimmer machines—you’ll have an easier time fitting in a graphics card, power supply, and other upgrades. If you find a small rig for a price that’s too good to pass up, it’ll work, but you’ll need to either shop for low-profile graphics cards or jury-rig it into the case using a PCI-express riser.

Finally, think about your upgrade plans for this machine. If you’re just building something cheap to get you by until you can build a new, high-end rig in a few months, you don’t need to worry too much about compatibility with future upgrades. But if you’re planning on adding a bit more power to this build, you may want to narrow your search to models that use a standard 24-pin power socket on the motherboard. Some of these office PCs use a smaller, non-standard 8-pin power connector, which means you won’t be able to upgrade your power supply in the future. It isn’t strictly necessary—many people will be just fine with the included power supply and a low-power graphics card like I’ll be using here—but it’s nice to have the option in the future. (There are 8-pin to 24-pin adapters out there, but I’m hesitant to use power supply adapters like these since many are cheaply or incorrectly made.)

That sounds like a lot of caveats, but as you browse through the shelves at the e-waste center (or through photos on Craigslist), you’ll be able to spot these things pretty quickly. I found a few contenders here in the San Diego area where I live, but eventually went with a Craigslisted Dell Optiplex 9010 that hit all my requirements for only $50. It didn’t have a hard drive, but even with that caveat, it was the best deal I could find—a hard drive is a pretty cheap addition.

Remember, patience is key—you may not find a killer deal tonight, tomorrow, or even next week, but if you monitor things closely and negotiate your butt off, you’ll eventually find the perfect system for an unbeatable price.

The graphics card

Graphic card on wooden table
For little money, the NVIDIA GTX 650 can get you a long way. Whitson Gordon

An office PC can handle day-to-day tasks just fine, but we’re gunning for a gaming rig here, which means you’ll need to pop in a dedicated graphics card. Again, you’ll want to hunt the used market for the best deals, and this is one area where e-waste centers probably don’t have what you need—but eBay just might.

On the low end, you can probably find an NVIDIA GTX 650 for cheap, as they usually sell for around $35 on eBay. It’s a bit long in the tooth, but you’d be surprised what you can get away with playing on a card this affordable—titles like CS:GO, League of Legends, and Dota 2 should run beautifully at 1080p, while games like Fortnite, Overwatch, and Rocket League may require ratcheting down the resolution a bit to stay at 60 frames per second. Something like this ASUS model is a good one to buy, since it doesn’t require a 6-pin connection to the power supply—which most office PCs won’t have.

If you can find it, an NVIDIA GTX 750 Ti would be even better, and is a good sweet spot for a build like this. It can crush most esports titles, and scrape by just enough in higher-end triple-A games. I found this Zotac model listed for $50 on OfferUp here in San Diego, which I negotiated down to $30—a pretty great deal. Again, the lack of a 6-pin socket is key if you don’t want to upgrade your power supply.

If you’re using a smaller PC, you’ll want a low-profile card—the NVIDIA GT 1030 is a popular one, and lies somewhere between the above two cards in power. It has a market price of around $50 for the less expensive models, but you might be able to get it for cheaper if you’re patient and buy locally.

The further you step up in cards—say, an AMD RX 460 or 560 for around $65, or a GTX 950, 960, or 1050 Ti for around $100—the more you can play. The 1050 Ti is also available without a 6-pin connector, and in a low-profile shape for slimmer desktops. At this point, though, you’ll need to consider adding a beefier power supply, which will increase the total cost of your setup. Still, a $200 rig powered by a GTX 1050 Ti is a fantastic value proposition.

You can go higher up the chain than that, but soon the old CPU in your salvaged computer will likely become a bottleneck, meaning your performance won’t increase enough to make the cost worth it. Plus, at that point, you’re probably better off building a PC from scratch rather than using the old office rig as your base anyway.

Other hardware (and software)

Computer components on wooden table
For security reasons, companies tend to destroy hard drives before disposing of their computers, so you'll likely have to get a new one. Whitson Gordon

If you have more to spend—or your computer comes missing a few components—there are a few other things you’ll need to consider:

  • Storage: Many of these used PCs won’t come with a hard drive, meaning you’ll have to add one yourself. You have a few choices: you can grab a new 500GB HDD for around $25, though it’ll be a little slow. If you’re efficient with your storage, I’d recommend buying a lower-capacity, higher-speed SSD like this 128GB PNY model for $20. Or, if you have enough money, get one of each: use the SSD for your boot drive, your spinning drive for your files, and live your best life. If you find a tower that does come with storage, make sure to test its health with CrystalDiskInfo—if it’s starting to fail, see if you can negotiate the price down further to make up for the drive you’ll have to buy.
  • An operating system: You’ll need a 5GB flash drive to install Windows—if you don’t have one, borrow one (you’ll only need it for an hour or two). Almost all of these PCs should come with Windows licenses in the form of a 25-digit key printed on a sticker somewhere on the tower. If yours doesn’t have a Windows license, it’s probably not worth buying, since Windows costs about $100 on its own. If you plan on running Linux instead, you won’t need to worry about this, but since most people will probably want Windows for gaming, make sure it has that sticker.
  • A keyboard, mouse, and monitor: As with most PC building guides, we’re only focusing on the tower itself here—we’re assuming you have an old monitor, keyboard, and mouse lying around. But if you don’t, you can often find old office peripherals in the same e-waste centers and classified apps where you found the tower (you’ll just need to budget for them). There are also plenty of affordable “gaming” mice and keyboards on Amazon, from brands like Velocifire and Redragon, if you’re willing to spend a bit more.
  • A network connection: My machine didn’t have Wi-Fi, which was fine since I planned on using the more reliable Ethernet connection to access the internet. If Ethernet isn’t an option for you and your PC doesn’t have Wi-Fi, you’ll want to find a PCI or USB Wi-Fi receiver to access the web, either used or new on Amazon.
  • A better power supply: while I found the 295-watt power supply in my Dell Optiplex was adequate for my GTX 750 Ti, it’s definitely borderline. If you can afford a nicer model like this EVGA 450-watt unit, it’s a worthy upgrade. Your system will be more stable since it will have more wattage headroom for your hardware, and you’ll have a wider choice in graphics cards, since it has a 6-pin connector.
  • Some extra RAM: If your office PC only comes with 4GB of RAM, you’ll be able to get by, but it’s really at the edge of what I’d recommend on a Windows system today. Luckily, those old PCs use the older DDR3 standard, which means you can probably buy another 4GB for $10 (or less) on the used market. You’ll be glad you did, particularly if you plan on opening a lot of browser tabs or playing higher-end games.

You shouldn’t need much else, though some rubbing alcohol may be useful for cleaning the case, and a cloth for cleaning any dust off internal components.

Make your upgrades and install Windows

Once you’ve got your hardware in-hand—remember, patience is a virtue if you want the best price possible—it’s time to build your PC. We’ve already run through how to build a PC in this guide, so I won’t hold your hand every step of the way, but I will note a few things you may want to watch out for with Optiplex-like office PCs.

Hand opening side of PC tower
Let's get the hard(ware) part over with.Whitson Gordon

I ended up with a $50 Dell Optiplex 9010 housing an Intel Core i5-3470 CPU, 4GB of RAM, and no hard drive. I added a GTX 750 Ti I got for $30 and an SSD I got for free from a friend who was leaving town—although let’s assume I paid $20 for the sake of a fair comparison. That comes out to $100 even for my final setup—though again, I’d recommend a bit more RAM and a new PSU if you have an extra $50 to spare.

My Optiplex was decently clean, though I did give the case a once-over with some rubbing alcohol and a microfiber cloth, especially where there was some leftover sticker gunk on the front. (Be careful not to remove that Windows license sticker, though.) I also removed the side panel, evicted some dust bunnies with a dust blower, and gently wiped off the fans with a dry cloth. If you have an electric air duster, all the better. (Canned air works too, though it’s terrible for the environment, so I don’t recommend it.)

Hand cleaning inside of PC tower
Ventilation fans tend to accumulate a lot of dust and are usually gross. Give it some tender love and care by cleaning it. Whitson Gordon

If you have a new power supply, you’ll want to install that before any other hardware. Unscrew the four screws surrounding the power cable on the back of the PC, unplug all the rainbow cables from the motherboard and hard drive (if applicable), and swap in your new one.

Next, grab your hard drive or SSD and insert the SATA cable, along with the SATA power cable from your power supply. I’m using an SSD, so I kind of just let it hang out where the DVD drive used to be, but if you’re using a traditional hard drive, you’ll want to screw it into the hard drive caddy and slide it into the cage. (Strangely, my particular Optiplex didn’t come with the blue caddy, but they’re available on eBay for $4.)

Hand inside of PC tower
If you're using a hard drive, don't leave it hanging—you'll want to secure it to the caddy with a couple of screws. Whitson Gordon

Finally, stick your graphics card in the top PCIe slot on the motherboard, making sure it’s firmly in place, and—if you bought extra RAM—put it in a free slot. Note that your RAM needs to go in the proper slot in order to work, so check your PC’s manual if you aren’t sure which slot to use—you can usually find it on the manufacturer’s website, e.g. Dell.com.

Hand inside PC tower
Yes, this all can look a little intimidating. If you need help, look for your PC's manual online. Whitson Gordon

Before you continue, you’ll want to use another Windows PC to burn the Windows installer to that flash drive using Microsoft’s Media Creation Tool. It’ll take a bit of time, so get the process started now and let it run while you perform the next steps.

Now you can plug your computer into the wall, connect your mouse, keyboard, and monitor, and fire ‘er up. Look for anything on-screen that says something like “Press DEL to enter Setup” or “Press F12 for Boot Options.” Press the key in question and enter the UEFI/BIOS menu—you’ll want to double check a few settings in here first. Make sure it’s set to boot using UEFI, not Legacy, and that Secure Boot is turned on (unless you’re using an operating system not supported by this feature). You’ll also want to make sure your SATA drive is set to AHCI, not IDE or RAID.

Screenshot of BIOS boot sequence
Get yourself comfy—there's going to be a lot of booting and rebooting at this stage. Whitson Gordon

When you’re satisfied with your BIOS settings, insert your Windows flash drive and reboot the computer. It should boot automatically into the Windows installer. Choose a custom install, erase your hard drive of choice, and format it for Windows usage just like you would any other new PC. When prompted for a Windows key, enter the one on your computer’s sticker. Even if it’s for Windows 7 or 8, it should work for Windows 10 as well.

The installation process may take a while, so make yourself a cup of coffee and try to contain your excitement. You’re almost there—once Windows drops you into the desktop, you can head to the support page on your PC’s manufacturer site (e.g. Dell, HP, or Lenovo), look up your PC model, and download any necessary drivers—usually Windows will install generic drivers to get you by, but grabbing the chipset, network, and audio drivers may be necessary if those functions don’t work (or if you want extra features contained in the manufacturer’s driver). You’ll also want to head to NVIDIA or AMD’s website to install your graphics card’s drivers, since they can improve gaming performance.

Screenshot of Dell.com
You're almost there, but nothing will work unless you get your drivers. Go to the manufacturer's website, download and install them. Whitson Gordon

Once that’s done, I recommend running a CPU stress test like Prime95 to make sure your computer doesn’t have any power management or stability issues, preferably alongside HWiNFO so you can keep an eye on your CPU temperatures. If it can handle an hour with Prime95 running and staying under 80 degrees Celsius (176 degrees Fahrenheit) or so, you should be golden. (If you do have problems, you may want to have to do some troubleshooting—you might need a new power supply, or your CPU may be dying.) You can also run a GPU benchmark like Heaven for a couple hours to make sure your graphics card is in good shape.

Screenshot of Heaven videogame
Congrats! Now you have a new PC to play with. Your productivity might drop a little, but hey—you're going to have a blast.Whitson Gordon

I know it’s hard to delay the fun, but if you can get through those stress tests, you can be much more confident that your PC is ready to game. When they’re finished, though, it’s time to play. Download your games and start with the graphics on their lowest settings, slowly ramping them up until the game becomes too choppy for your tastes. With a bit of careful tweaking, you’ll be mowing down alien invaders in no time.