1. Under the hood, how much of a differance is there between xp and 2k
Virtually none that matters. For all intents and purposes, XP is an updated version of 2000. Things like added compatability, eye candy and security updates.
2. does xp have more 9x components in it than 2k?
The XP codebase is very similar to 2000, I don't think there is any "9x components" at all. Making XP more compatable with more software and hardware doesn't require adding components of 9x into it. At least not from what I understand.
3. Is windows2k still faster than xp even with the latest drivers and service packs?
The OS is virtually the same. Turn of Windows XPs "eye candy" and you have 2000. The speed should be the same in an otherwise identical system. Other than bootup that is. Windows XP has significant advantage here and boots up much faster than 2000.
4. how much more memory does xp use than 2k?
In an otherwise identical system, with XPs eye candy off, I would bet about the same.
\Dan