NVIDIA rolled out GeForce 177.92 beta drivers for Windows XP and Windows Vista, you can grab them over here. I haven't tested the driver but if the information in the release log is correct this driver should give NVIDIA's cards a much needed performance boost.
There are performance gains for single GPU and SLI setups, the most notable improvements are 15% gains in Call of Duty 4 and Bioshock DX10. Crysis isn't mentioned in the changelog, looks like they couldn't squeeze more performance out of that game.
Here's the changelog of the Windows XP driver:
Supports GeForce 6-series, 7-series, 8-series, 9-series, and 200-series
GPUs, including the newly released GeForce
9800 GTX+, 9800
GT, 9500 GT,
Adds support for NVIDIA PhysX
acceleration on all GeForce 8-series, 9-series and 200-series GPUs with a
minimum of 256MB dedicated graphics memory (this driver package installs NVIDIA
PhysX System Software v8.08.18).
Experience GPU PhysX acceleration in several full games and demos today by
Adds support for 2-way NVIDIA SLI technology with GeForce GTX 200-series
GPUs on Intel D5400XS motherboards.