XP

Screws sometimes have a somewhat limited durability. The more often you unscrew and rescrew something, the more likely it is that the screw will become stuck. This is especially the case for those small cheap aluminum screws that are secured very tightly. The more you try to remove it, the more you'll end destroying the drive, the part where you stick the screw driver into.

A screw that has been damaged to the extent, that it is impossible to remove with a screw driver, is known as a stripped screw.

This is where a left handed drill bit comes in handy. It is THE best method to remove a slipped screw and it hasn't failed me once. Your basically going to drill into that screw until your drill bit grips it and pulls it out.

(Having a pair of pliers on hand can help you remove the screw from the drill bit without damaging it)

It is also much easier then any other method available.