A properly set up XP machine always seems to run just a little bit nippier than 2000 in my experience, although its a fairly small difference. The main thing that slows down XP is a lot of the fancy graphics, but even then, if your machine is quick enough you wont notice. And for the LCD monitor users out there, theres "Cleartype" font smoothing, which makes fonts look pretty good on an LCD screen. You can also use it on CRT screens, but I didnt quite like the effect on CRT. Personally, if your happy with 2000, it doesnt really seem worth the effort to re-install with XP, as it may cause you problems (probably not, but you never know), and the only reason to get it is for the extra polish really - I'm not sure why people have a downer on the way XP looks and operates, but even my parents can use it, and for me, that says a lot about its ease of use over previous versions.
