NT is a somewhat generic term that can refer to either the Windows NT series (3.51, 4.0, 2000, XP, etc.) or to specific versions that used NT in the product name (pretty much just 3.51 and 4.0). NT 3.51 and 4.0 were based on UCS-2. It would probably be more accurate to leave the "NT" out entirely, since the "2000" and "XP" stand on their own (not to mention that NT does not apply to CE).