vista - started getting unplayable performance

I posted this over in the graphics card forum as well.

I have a pretty decent rig:
core-duo x6800 at 2.93
2 gig on memory
intel 975 badaxe mobo
nvidia 7950gx2 video card
vista ultimate

system was working fine. I was most recently with halo and graw2 with fine performance. One day, my pc boots to black screen of death, and I had to reinstall Vista.

I slowly start to get my apps back onto system and buy Bioshock.
It performs so bad, but it isn't playable even at lowest video settings(mouse jerky...). I just assumed it was some tweaking needed for Bioshock.
I finally get GRAW2 back on system and it has the same problem. For example, starting a new campain and the video cut-away where the helocopter takes you around a mountain takes FOREVER and some times crashes.
GRAW2 used to play great!

Any thoughts?
There are some data points on the web about a microsoft update causes vista to eat more memory than before. I think my 2gig is fine. I can monitor task manager on my other monitor while graw2 runs, for example. Memory is fine, but cpu usage goes up to around 100% and stays there.

I tried various nvidia drivers including:
1) the one a used before install
2) the one recommend for bioshock that fixes some issues with that game
3) the relatively new microsoft certified one.

thanks in advance!