I noticed when I installed Vista the other day with the 169.35 drivers that Quake 3 has problem changing the gamma. I remember the same problem when I installed XP sometime back in 2001. Thankfully, id solved this in later patches. But again I see alot of people having these types of problems. I looked at different forums and to my knowledge there wasn't really a decent fix for this. Some said setting r_ignorehwgamma to 1 made it better, but not not much imo.
I also remember when I had this issue with xp that if you set the game to run in compatiblility mode to win98, it looked better. So I tried this in Vista and sure enough the gamma issue was fixed. But another problem occured, the game wouldn't run past 60fps. I'm running with a LCD display. I thought I somehow set the r_finish to 1, or r_swapinterval to 1, but I hadn't.
What struck me was that I couldn't remember having a gamma problem with Vista before, prior to nov/dec 2007. I guess it's a driver issue.
So I looked through the Nvidia control panel, and tried out different settings. The solution is simple.
In Manage 3D Settings / Vertical Sync, change it to Force Off.
Now the game runs smooth again.
I'm guessing this applies to most openGL games including COD.