AMD64 3400+, 1 Gig DDR, SATA
But even that isn't enough to play the last mission without swapping. That's with custom media VPs though so the official ones may or may not have the same memory usage there. My VPs are cut up so that all models and all textures they use are in on VP, all effects are in one VP and all other upgraded textures are in another VP. It's easy to just move the hi-res effects out of the way an save memory that way or move the additional textures VP out of the way. That can cut the final missions memory usage by about 30 to 40 % and it's much more playable that way.
I do tend to play in a window with several terminal windows, Evolution, Firefox and Anjuta always running though so that eats up a bit of my memory that could otherwise be used for the game.