winxp or win2000

[colonel]

I tried request.getHeader("User-Agent) on my homepage(in JSP).
This is what I got for windows XP:
windows NT 5.1

I am confused.
what result will you get for windows 2000? is it NT 5.0?what about windows server 2003?
It seems windows server 2003 will be the same as windows xp.

please help
thx