Cant play any non valve games on steam

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?

It will be something with your system, as I've been able to play FM11, Sims 3 etc on mine with no trouble. Might be worth deleting blobs.

On a odd note, football manager still runs completly fine?

Sorry I forgot to post u the windows disk :P

Ill send it when i get home on monday :)

Delete ClientRegistry.blob

DE@fail.org :D