It's worth knowing that while some 1.0GHz P3 could give it a little extra kick it won't bring it close enough to run today's monster games.
I'd stick with kicking it up to 512MB RAM and seeing if it has at least a 7200 RPM hard drive.
I have a Dell Dimension 2100 purchased about 5 years ago. It has a 1.10 Ghz Celeron processor, which really sucks, so I'm looking tp upgrade. I was just wondering, what processor would be best for it? Also, I don;t think I have to, but would I have to switch motherboards if I switch the CPU??