Low Fps on Win 7

I have a really bad problem,when i have on the screen more than 3-4 mosnters my fps drops really bad 15-20 fps,i just can't go in mk,i get 2-3 fps:(,i have a 8800gt video card,2 gigs of ram,amd 5000+ oc-ed at 3.0ghz,and the latest gpu drivers (185.)

i can't play conquer lol

edit: i have win 7 ultimate build 7077


in other games i dont have problems(grid,farcry2,spore,counterstike)

get the RC now

awww, i can't afford to reinstall the OS,i need to do school projects:),i will try that in some day,thanks!!!

up!