There are no nVidia video drivers for Vista that support SLI.
You will have to wait til nVidia release a "vista"driver for SLI.

"Thanh Ha" wrote in message
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I have 2 x 6600GT and Vista build 5840. Driver version is 96.85 from
www.nvidia.com. How do I now if my VGA card is running in SLI mode or not?