Thanks for your replies. I tried turning up the shaders and shadows, and it does look a lot better and doesn't freeze up like it was anymore. When I turn on the framerate display, it comes up with a memory usage stat, and I noticed that in some forests it would reach >1gb of memory.
Right now the memory I have has fairly bad timings (A-Data 2x1gb DDR2 800 5-5-5-18, I think) so I don't really need high performance memory - IIRC anything faster than the slowest chip is slowed down. Fairly sure motherboard support stops at DDR2 800 also.
I was looking at this 2x1gb Wintec
ram package, but was also debating about spending the little extra for this 2x2gb
package. I realize now that 2gb is too low to play Crysis, but would I get much of a benefit by going past 4gb of memory? I primarily use a 64-bit OS on the computer, so that shouldn't be an issue.