Well, I don't know much about motherboards. I looked into replacing it at one point, but quickly became so confused I dropped the whole idea. I can add RAM, and replace something like the video card or cd drive, but that's about as far as it goes. All of my RAM is PC100 SDRAM, but thanks for the advice.
For the most part, I just play wargames and turn-based stratgy games, so CM (and soon CM:BB) is the only game that really taxes my system. IL-2 Sturmovik looks interesting, but I'm doubtful my system will be able to deal with it, even with a new graphics card.