I think the two best operating systems that Microsoft developed are Windows 2000 Professional first, then Windows XP Professional second. For modern hardware, Windows XP Professional is better due to wider hardware support.
I’m sticking with Win2000 Professional. It’s been the most stable and user friendly OS yet, by Microsoft that is. I had Win.XP Professional and removed it to put in 2000. I haven’t regretted it for a second.
Everybody I know that bought a new computer with Vista has had it taken out and XP or 2000 put in.
The next computer I build will probably have Linux in it.