CE, NT, and ME shouldn't be counted in the main series because those are specialized versions...or maybe it was 2000, not ME, but i know one of those two are server versions of windows, just like Windows Server 2008. i think NT is server too isn't it? not 100% on that. and CE is portable, which shouldn't count.
There are server versions of 2000, but there is a non server version too...
Windows ME wasn't a server version and I think NT was more aimed at businesses.
http://en.wikipedia.org/wiki/Windows_NTCE was used for the Sega Dreamcast
But that was only for some games and it isn't stored on the console itself.
NT had client and server versions. In fact, XP is based off NT.
Pretty much every version of Windows since Win2000 is based on NT.
ME was the last 9x version of Windows that tried to restrict access to DOS to speed up boot times and was buggy as hell.
I've never used ME, but apparently my mum installed it when it was near new and almost immediately removed and sold it...