If you think your PC has the balls to run Crysis at its very highest settings, then there's a small article over at Planet Crysis that you should read.
Okay, when I say "very highest", I'm not talking about moving all the in-game sliders to the far right. To see what pain Crytek's shooter is truly capable of dishing out on your humble PC, you'll need to dive into the game's configuration files and tweak a few settings.
The Planet Crysis article has everything you need to know, but if you're not as well endowed in the sack department as your machine is, there's a download of the altered files available from Crymod.
You may have seen similar settings floating around the Internet; these are the most up-to-date.
If you haven't already, you might want to tweak Crysis first to get it running at its best performance-wise, or if you're running Windows XP, enable those lauded Direct3D 10 "Vista-only" features.
Ultra High Quality Custom Config [Planet Crysis]