Ummm, all things being equal XP and 2000 should be just as stable as each other. I've had 2K server stay up and serve well over 200 clients for several months on end, but it had to be set up right (bear in mind 2K server is mostly just 2K with a 'server' sticker on the box ;-)). XP can be equally stable, but boots a whole lot quicker!
I'm posting this on my XP machine, which runs a half dozen different database systems for testing purposes, several patches to make Windows look better, and loads of network admin tools, and it hasn't blue-screened on me in 23 months of use. I'm using the same drivers that I started out with, and have used a USB scanner, joypad, mouse, memory stick and CD Writer.
I hate using Windows, but the reliability problems of Windows98 arn't an issue any more - when it's done right! Windows95 used to run nicely if you re-installed it every 6 months ...