I have a 2.8ghz machine, 1 gig of ram, and a new video card. I run with winXP. I have a couple of distinct slowdowns -
menu screen buttons - delayed clicking (not that bad)
right clicking on a unit for info - 2-5 second delay (painful)
screen scrolling delay - when my mouse hits the very edge of the screen to scroll, there is a full second delay before it actually starts to scroll. (very painful!)
animation delay - explosions (like grenade launcher) draw very slowly. solved easily enough by taking "animations" slider to zero.
I've tried setting all of the delays to 0, even in the .ini file. Everything runs very smoothly except for the things that I mentioned. Ive tried running in both screen modes, directx and the other option, no difference in any of them. I've made sure to not start any other programs before starting the game.
This is frustrating. I absolutely loved SP2 when it first came out and am really itching to play