I have tried and used all microsoft OS availible except Win2k Advanced and Database Server and the new Windows (- NT that server thing - to tell the truth I didn't give it a damn).
Most of what I tried was warez - in Hungary you can't really afford 150$ for your OS.
Don't ban me please - I'm actually one of the "idiots" who use a legal windows here.
My main problem with Windows XP was its ridicoulus activation and its allergy to any hardware modifications and it inflexibility to running a multi-boot system with several OS.
The user interface was over simplified and all the converstaion dialoges and pop-ups rather prevented me from working.
Win95 was great by its time.
That was a long time ago....
Win98 was annoying with its poor memory management and inconsistent control panel.
Moreover it was really poor at multitasking.
The reason for this was the pure fact that it wasn't a preemtive system, so any program could go on rampage.
Avoid Windows Milenium like plague it's Win98^2'nd incarnation
One thing that bugs me about all Windowses is the fact that instead a unified user interface you have to manage your explorer, the control panel and the built in security tools to fine tune your system.
Win2k so far is the most stabile and user (experienced user, not your little brother/sister type who knows to get you whenever, he wants to install a game) friendly among the windows OS I tried.
Actually there's not that much difference between Professional and Server - through a strange turn of fate I'm running a Server right now - except that you have tools to properly manage the Active Directory.
BTW that's the whole concept on what windows servers are keen on, and that's the reason I support Linux for most of the system people want to set up.
A windows server would benefit a small office, but I hadn't seen it in action like that, so I keep my wits about it.
Moreover your integrated software has some little adjsutments to help you, but I still have to stay that Win2k is a stabile, but definitly not 1'st grade server material.
Go for Linux or Unix if you want something truly set up for a webserver.
I hadn't use XP too much, the main problem as I said earlier that user interface actually covers the OS so much that it can be really hard to do things.
Thankfully it can be disabled, so listen to other people that OS may still have merits over Win2k.
I had trouble with the activation, and the stupid way it handled some thing coming from win2k - Did you know there's always a built in administrator account beside your own? I guess most of you knew - but it bugs me since any ordinary user wouldn't have a clue about it.