Re: comp slows way down...
Hmmm, don't know. Specs look just fine there. Isn't that system equipped with Intel Extreme Graphics? I heard those are pretty sucky. It's good that you got the RAM bumped up to 1GB and a P4 CPU. Try doing a disk cleanup and defrag. Upgrade to a new video card or bump down the settings to the game. At the last resort, you can try to reinstall it.
The Dimension 2400 is the lack of upgradeablity. No AGP port is available, meaning that you will have to settle for the built in Intel Extreme graphics, which are fine for normal usage, but cannot handle 3D games or multiple monitor use. It is possible to buy low end 3D gaming cards in a PCI format, though they can be hard to find.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?