I've heard that as well, I think just a VGA to your primary monitor, assuming you're using the DVI for your graphics. You don't need a second monitor.
I'm surprised Nvidia haven't found a way round this yet, but it's something to do with Vista not liking to use a gfx card that's not connected, even though it doesn't technically need a connection to do what it's doing.
Work around is easy enough.
Joe
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