I am a computer helpdesk technician by trade.
running 2 PC's with one on Nvidia and one on ATI video cards, both win 7 64 bit, both run smooth as glass on this game, not a single crash.
It's not the game
I am running the Steam version that auto patches itself, maybe ensure you have all downloads/ patches released for the game installed, update DX and video drivers, run windows updates too.
ensure your not low on space on c:\
Run an updated virus scan or spybot scan (both is best)
remove any strange programs that you never use and dont recall ever installing / needing. (Ask , seek, Conduit engine toolbars and the like for internet explorer is a classic example)