You guys are quite right, I am on vista with an SLI board. Used to run 9800GT's in SLi but found a deal on a 4890, so I sold one of the 9800GT's to pay for part of the 4890. Wanted to use Quadruple monitor without having to switch out of SLI or losing similar performance. Now I'm back to 2.
I've formatted this computer with Windows 7 some time ago, but I took out the hard drive to use it with another computer.
I'll re-migrate to Windows 7 when I have enough space for another partition. May be a while...