I've never been infected in my 15+ years of computing, but once NAV found & quarantined a virus in a file I downloaded on Kazaa.
All versions of Windows after ME are based on the NT code base. 95, 98 & ME were non-NT versions.
I've used NT 3.51 & 4.0. I'm guessing there was a 1.x & 2.x at some point?
Windows 2000 is just a 'cooler' name than NT 5.0, then they continued to use 'cool' names instead of Windows NT x.0