Well, I have:
Intel C2D E6850 (3Ghz)
2GB DDR2 800Mhz
Geforce 8800GTS 320MB
It recommends MEdium spec, but in the demo, despite the corruption i get, it seems playable on the highest setting....in WinXP.
I think the only problem i have is the card i have, it only has 320MB, where i believe it recommends 512MB or more.
But its very playable for me on high.
The settings in xp can be forced to very high you can download my settings.cfg on the message I posted. It is just as good as high on 1024x768 i get 26 to 32 fps and the game uses just under a gig of ram. use the 169.03 beta drivers for good results.