I really liked Win2KPro. My son has a copy of Windows Neptune he fires up now and then.
But I also had lots of fun when Code Red and Nimda came around - full perm file navigation on computers everywhere. Any Win2k box knocking on my firewall was telling me it was wide open for use.
I remember building a lc for a client, installing 2k then SP2. Clicking around installing our software thinking “this could be my main machine. This would be good”
Then it got a virus.
30 minutes after I finished installing windows.