Urm, well i'm running the 170 Nvidia drivers with my Geforce 8400GS, and i'm getting 30-35fps average using 1024x768 resolution and medium settings, which ain't too bad considering the card is a little weak. I plan to upgrade to a 9600GT during the next few months.
Oh and correction: It is not the game developers fault that the new Nvidia drivers may have a slightest incompatibility issue with their game (which after all, is only a very minor problem from the sound of it). It's up to Nvidia to fix this, and i'm sure they will. I just LOATHE how quick people are to lash out at game developers when issues are not always THEIR fault. Halo 2 for PC is reasonably well debugged, I've certainly found no major flaws with it, and it has also received a modicum of patch support following release, it does not necessarily require further treatment.
Especially since it is quite likely at this point that Microsoft may be thinking of working on Halo 3 for PC, as the leaks suggest.