Ive been having massive problems playing or running any game on steam that i have downloaded that isnt valve made.

Every time i load one of them up ( CIV 5, GTA for example ) nothing will happen and a pop up will come up saying the game has stopped working.

Ive tried almost everything i can think of, reinstalled the games, reinstalled steam, turned of the DEP, changed the steam folder name, run as admin, validated the files, i cant think of anything else to do but a complete reformatting.

Because i dont want to do that at this moment in time, any other advice?