Win2KPro was the peak. Windows 7 wasn't terrible, and you could select the Windows 2000 UI. It's been downhill since 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.
Then it got a virus.
30 minutes after I finished installing windows.