For the past few days, my computer has been acting slow. I believe my computer is a "decent" computer but whenever I start up a simple game such as counterstrike 1.6, I get so much lag. I tried to see if it was the game itself thats the problem by playing other games, and turns out that it all lags. I tried restarting, deleteing some files that I downloaded before, scan for viruses, nothing.
See if you can do a system restore, i had a problem like that last week(15FPS is CS 1.6 with a 4850 is BAD), rolled it back a week and it is working fine now. Not sure what caused it to misbehave but the system restore fixed it.