I am thinking of buying it.
Windows 7 Home Premium 64-Bit
4 GB RAM
Intel Core i5 CPU 2.67 Ghz, 4 cores.
1 TB Memory
MSI R5770 Hawk Radeon HD 5770 1GB 128-bit Video Card
Also since we are on the topic of computers I am thinking of buying 4 more gigs of ram, I can just plug them in like the first 4 right?
You shouldn't have a problem imho, but I would highly recommend switching it to DirectX9.0c instead of the DX10. I decided to buy crysis for myself when it was on sale on steam and ran into problems on the last level. My graphics kept freaking out and I couldn't play it at all until I went to the config window forcing it to go to DX9.
Running a system that seems a bit similar to yours the only difference being I have a core i7, 6 gigs of ram, and the 5870 ATI card. Running W7 64bit ultimate, but I doubt that makes any difference in the game. With everything set to max i'll average about 45 to 50 fps sometimes up to 60fps+ if I get lucky. Though I will get bogged down during the higher end graphical sessions.