You’ve finally got your PC set up to your liking and running smoothly. So when you decide to add software later on, the last thing you want is something potentially unstable that could endanger the system. Although they’re not a replacement for antivirus applications, virtual machines can really come in handy. Essentially, they’re full-fledged operating systems that run as an application inside your actual operating system while remaining safely isolated from it.

Say you want to open a file you downloaded from a questionable source, kick the tires on a new operating system like Linux, or even run an older OS from the familiar environment of your main desktop. If anything goes awry in your virtual machine, you can reset it to a previous state or just delete it altogether, with no harm to your system. You could even run a separate operating system as a virtual machine just to use that one killer app that’s not available on your OS of choice.

Free applications like Microsoft’s Windows Virtual PC ([micro](http://micro/, VMware Player ( and the open-source app VirtualBox ( are great for getting your feet wet. Setting them up is a similar process to installing a regular operating system. Once you’ve done it, it will seem like you’ve got a real, separate computer living inside your system.