P4 2.4Ghz
1 GB RAM
ATI Radeon 9600 Pro O/Ced to 432/700
250GB HD
Audigy 2 sound card

It runs great at 10x7 with large unit size. I'll get the occassional lag with more than 3000 units on the map (I agree it must be the CPU) but other than that the game runs great. BTW, I had a GF3 prior to purchasing the Radeon 9600 Pro and the difference in graphics is very noticeable. RTW definitely uses DX9 shaders, because the body form and armor of units look more realistic and smooth than the DX8 shaders under my GF3. It's a nice bonus after my GF3 fried during a PSU overload :(.