in my opinion winxp is to win2k what winMe is to win98.
It's just the same OS with better asthetics and a few more features. They're both reliable, but I prefer winxp. win2k is supposed to be a little more suitable to people who are hands on and dig into the OS. 90% of the drivers that work with win2k work under winxp... but not everything is compatible in both. If you like the glossed over features of XP than get it... if you like function over form than win2k is an acceptable alternative.