I downloaded Fallout New Vegas from Steam and I have not been able to play once! I have uninstalled and installed several times. Each time I press play from the launcher, the game immediately crashes. Is there any way I can get this to game to play?

Stats:
Intel Quad core 2.66 Ghz
Windows Vista Home Premium 64bit
ATI Radeon HD 3850 1 GB
8 gigs RAM

If it helps I have had trouble updating my Realtek High Definition audio driver, plus, the ATI Radeon audio update fails during install. I am not sure if those affect the game.
Please help.