Hmm... for everyone who's saying that Win2000 is more stable than Win98SE... I don't really think so. I usually end up having the 2000 machines here hang (hang meaning I have to wait a few minutes for Ctrl-Alt-Del to let me log off) about once every two hours on average here. My Win98SE machine at home I would get a BSoD about once a week (and that was about 30 hours of use). The only thing that's really "stable" about 2000 is you can usually get away with logging off, and logging back in (USUALLY... I've had to cut the power a few times).
XP Pro, while I haven't used it for as much time as the others, I haven't crashed yet. And I've tried a few times

XP Home, I've managed to hang quite a few times for the short amount of time I was playing with it.
But, overall, I still prefer Win98SE. I don't know of any programs where you can run it on one of the newer OS, but not on 98SE. I know where most of the settings/customization is (I won't say all, because there's probably some obscure thing that I would never use that I don't know about), and it's easier to change settings than the other ones. After all, "user-friendly" implies methods to prevent "user stupidity", even if they really did mean to change that setting.