[quote='Icetech',index.php?page=Thread&postID=75339 #post75339]Its not nvidia's drivers.. its vista.. we noticed the same things with ati cards on systems we build for customers.. all our gaming systems stay XP for now...[/quote]
I'm not an expert about this -- I don't even use Vista. But my impression from reading hardware review sites is that this difference has disappeared. Back when Vista first came out, the review sites generally found that on average, Vista was a little slower in games. But more recent tests show that Vista has caught up.

I don't have time now to do a whole lot of digging in Google, but here are two links that give the general idea. They show ExtremeTech's comparisons of XP and Vista for game speed. The first link shows benchmarks from when Vista first came out. The second link shows last month.

[url='http://www.extremetech.com/article2/0,1558,2096940,00.asp']XP vs. Vista Game Performance, Feb. 2007[/url]
XP vs. Vista Game Performance, May 2008

Here's how ExtremeTech summarized their findings in the more recent article:

Quote Originally Posted by ExtremeTech
If you were expecting a huge drop in performance as your eyes scanned from the XP to the Vista results, well, surprise! As many a tech analyst predicted, Windows Vista's gaming performance conundrum has largely been solved, and it was mainly due to early graphics drivers.

In fact, I'd been planning to run a few other gaming tests, but the results from these were so uninteresting that further work didn't seem merited. Love it or hate it, Vista is performing far better than it used to.

Game performance, it seems, has been exorcised from your concern when choosing a Microsoft operating system. That leaves a few other factors, of course: stability, responsiveness, eye candy, price, DirectX version, and a few other odds and ends.

It took about a year and a half, but the performance gap between Vista and its forerunner has finally evaporated.