Driver Issues/Extreme computer slowdown

Hi, was wondering if anyone could give me some input on a bizarre problem thats started recently. I started getting that n4_disp.dll problem with my nvidia drivers, and after several reinstalls of the driver software, some games are acting like the computer's resources are all locked up e.g, Oblivion went to 1 frame every 4 or 5 seconds. Also, in explorer, the cursor sometimes is very lagged out and has a 3-5 second delay when moving it. I had gotten some drivers from guru 3-d which install properly but on restart the computer cannot ever complete successfully so the drivers are always gone when i hard reboot back into windows. Is this a possible hardware issue? I've taken this to Best Buy and all they did was try to sell a new computer;(