Im running XP pro, but I think 2000 is almost as good, without all the eye candy and some OS components. With some additional tools you can get almost all of the XP features. Plus doesn't take as much memory as XP. I think they both use almost the same kernel. 98 is still good and it runs super fast, but it's starting to show it's age, espscially multi-media-wise.
I have almost all versions and I never even think about ME when I need to install Windows. I'm also learning Linux.