Laptop computers used to run on nickel-cadmium batteries, which experienced the "memory effect," where they lost capacity over time if recharged before they were drained. That's no longer the case. Newer laptops use lithium-ion or lithium-polymer batteries. Repeatedly discharging the battery to zero doesn't help a lithium-ion; in fact, it will probably shorten its overall life and capacity. The only situation in which you may need to intentionally deep discharge your battery is if its built-in digital fuel gauge, which tracks the remaining battery power and reports it to your computer, gets out of whack as a result of long-term storage or heavy use. Some computers have built-in calibration tools, but if yours doesn't, charge the battery to full and then run it down to zero by disabling power-saving profiles in the operating system.