If you are running some of the recent Geforce 6 series cards or even the Quadro gfx card you might be interested in the 71.81 WHQL drivers that have found on the web. Enthusiasts are seeing a 8-12% gain on 3dmark2005 and some issues have been fixed on Halo.
Since these are "leaked" we suggest that you use and abuse at your own risk!
"These drivers are date stamped at the 28th of January 2005 making them the absolute newest set to date. Furthermore these drivers WHQL (Microsoft tested) signed. We recrunched the driver set towards a lovely 15MB. It includes the easy to use setup.exe for easy installation."