Windows® 98/ME/2000/XP: 400 MHz Pentium II or equivalent 128 MB of RAM 8 MB 3D video card (TNT, i810, Voodoo 3, Rage 128 equivalent or better) with DirectX® 8.1 support 700 MB HD space 4X CD-ROM drive
Recommended: 600 MHz processor 256 MB of RAM 32 MB 3D video card DirectX® 8.1 compatible sound card
Also in my experience in running the game I would definitely suggest that you get a new machine completely.
Recently I easily built a quality new machine for $650 however with no monitors, less than average video card, no sound card and only 256M of RAM.
However with a quality graphics card, 512M of RAM, 17" Monitor, and basic SB Live! or other sound card you should be able to build one for around "200 or so. Post back.
I'd recommend DDR RAM, since they stopped making SDRAM the price has started to rise and will continue to do so (just look at the prices of EDO these days). So SD will cost you more but perform worse than DDR.
That is worthwhile knowing - I thought SD would become "cheap as chips" pardon the pun - once it started to become obsolete but as you say the opposite happens.
I will then purchase a mobo that fits DDR - good man.