mikhael, no offence but your advice is not good.
I've been running WinXP for many months now, and I can honestly say that XP is better than W98(SE), ME or 2k.
Of course everyone has their own opinions and experiences with each OS, but for me XP has been the best. I haven't encoutered any major bugs, most have been already fixed (windowsupdate).
Of course a better advice is to wait for SP1 before buying XP.

No OS can be perfect for every system, that is PC's achilles heel.
For example, WinME can work like a dream for some few systems, while being like a nightmare for most.
But I can say that I won't change back to W98 or W2k in any case, and I am happy when SP1 comes out and fixes the major bugs, even if I haven't encoutered the bugs.