It requiers good CPU & much RAM. You also don't need high end graphic card to play it on ultra high. If you also have dual core cpu with ~3ghz , 3-4 GB RAM and GeForce 8600 GT you can play the game on very high settings.
Like i said in another thread that have nothing to say. With minimum requiriments it will be unplayable and will look terrible. Recomended are somewhere ok but are anyway not realy right, you won't be able to play the game on high settings with just 2.5 GB RAM, rest should be ok. Also it is enough to have dual core with 2.8-3 GhZ or quad core cpu with 2 GhZ or more. (Quad Core CPU's will make your FPS 2-3x higher than dual core with higher frequency. Dual Core CPU 3.8 GhZ 20 FPS , same system just CPU changed to Quad Core with 3.0 and you will get 45-55 FPS.