Oh ok... not a desktop... ok... Most of the time its a desktop with the soft case metal causing issues.
Laptops are more tricky as for you dont want to have metal filings or fragments making their way inside.
If the screw is close to the surface and you can grab it with needle nose plyers, you may be able to twist it counter clockwise and once it starts to move you might have something left to use a screw driver with or else its needle nose the whole way out until finger tight in which you can unscrew with fingers.
If the screw is a deep screw such as down in a 1/4" hole and stripped, this is one of the worst ones to be dealing with and extraction is a pain.
If the screws are screwing into metal usually brass ferrals which are in the cast plastic, the only way to get it out is to carefully grind the top of the screw off with a dremmel. This then allows for the cover to slide off of the screw body with no screw top/flat holding it together. You then can remove the remains of the screw by plyers to unscrew it from the brass threaded ferral that is fused to the plastic body of the laptop. ((( The extreme caution with this process is that there are metal dust/fragments that you do not want to have making their way into the computer case to short out sensitive electronics )))
If the screws are threaded into plastic directly, the trick to getting these out is by heating up the screw with a soldering iron and once hot grabbing the screw top and pulling the hot screw out of the laptop in which the plastic that is around the metal threads of the screw is melted.
However... Its far more common that the screws are threaded into metal on the inside of the laptop instead of threaded into plastic. But one way to know what type your dealing with is to look at the other screws that are like it that you already removed. If the threads are large and less per inch, then its a self tapping screw that goes into a plastic stand off inside on the opposing case cover. If you are looking at very fine threads on the screws which is more common, then its a metal screw that threads into a metal piece on the inside of the case, and this can sometimes be threaded into the keypad frame.
*** If you are going to use the last effort dremmel attempt to cut the top off of this screw.. Here are the steps I took that have been successful.
1.) Tape over all vent holes etc on the case so that no metal frags/dust etc can fall into the inside of the case.
2.) Have a Vacuum cleaner handy as well as a dremmel with a grinding stone at the tip of it that is rated for grinding steel.
3.) Remove Battery and Hard Drive ( if one that can be removed from a bottom access panel ) To avoid the hard drive getting shocked by the vibration of the dremmel.
4.) Carefully with safety glasses on hopefully, and maybe even a flash light to see into the hole, carefully grind the top of the screw, and alternate between grinding and vacuum to suck out the dust. * If the screws are steel, you can also magnetize a nail or use another magnet to get the metal filings to cling to it. *** Just be sure the magnet never gets near the HDD.
5.) When the screw top is removed and all fragments are carefully removed, the laptop cover should come off.
6.) Measure the length of the screw that was destroyed to try to find a suitable replacement with same thread count and size, or if its an optional screw leave it empty when done.
7.) Also remove the tape that was plugging all vent holes etc as for the tape served its purpose to block entry of fragments into the case and is no longer needed.
This is a very risky process... Perform at own risk. I have had to do this before with a clients laptop that their son rounded the philips screw when trying to add memory to laptop by using an over sized screw driver on a jewelers philips type screw. Fortunately because I have various dead laptops around, I was able to test this on a carcass first and then perform this on the clients laptop, and also had an abundance of similar screws to take from a dead laptop and install as a replacement screw to this laptop.
