We tried to play Crysis on a DirectX 10 platform with a machine with 4GB ram and Vista 64 bit and we've learned that at high or very high settings, even at 1024x768 or 1280x1024, you get less than 20 FPS. We used the best card on the market, an 8800 Ultra overclocked all the way to 655MHz, and it still scored some 16.5 FPS average in a benchmark. We tried to turn the FSAA and Aniso off and it still didn't help much.
The test machine is powered by two Athlon FX 74, 3GHz dual core CPUs, has 4GB of memory, and the above mentioned Geforce 8800 Ultra, but this is just not enough; and even at modest resolution it cannot play Crysis. I guess you can blame Nvidia’s 64 bit Vista driver.
We installed the same demo under Windows XP and we upped the FPS rate all the way to 36.5, which is enough to shoot and kill the bad guys. This is more than two times better.
If you don’t have Vista 32 bit, go for Windows XP and it looks the same and will work better. SLI still doesn’t work on the Crysis demo.