To be able to use SLi successfully on these chipsets, you need this nVidia Geforce Driver: ver. 275.50 available here..
Win7 x64 / Vista x64: http://www.nvidia.com/object/win7-winvista-64bit-275.50-beta-driver.html
Win7 x32 / Vista x32: http://www.nvidia.com/object/win7-winvista-32bit-275.50-beta-driver.html
WinXP: http://www.nvidia.com/object/winxp-275.50-beta-driver.html
WinXP x64: http://www.nvidia.com/object/winxp64-275.50-beta-driver.html
There is also a 275.50 (whql) out, it does NOT support SLi on AMD chipsets, you must use the "beta version" above, other than it adding support for SLi on AMD 900 series chipsets, it's the same driver.
Just thought I'd let anyone that needs them know...