Thank me that I'm back lol.
OK a fall system retore is basically starting everything back from scratch. Back to factory settings.
So in English, Your comp will be back how it was when you first got it. Yes this means your lose ALL your files but its for the good.
To do a fall system restore find a O/S disk, example XP, Vista, Linux. Place the disk in your comp and reboot it. It should come up about reinstalation. Do what it asks abd your set to go... make sure you know your Serial code, it should either be with the O/S package or printed on the computyer.
P.S. if your comp has a system restore partiton just press F10 while its rebooting. But for the sake of it just follow the above bro.
~Be Cool~