Unable to Uninstall .NET Framework vers. 2 and 3

My "Add/Remove Programs" function in the Control Panel does not remove .NET
Framework 2 and 3, for some reason. I made the mistake of installing these
versions (don't ask me why, please). I can't do a restore because I will lose
data that was added since the installation of the unwanted .NET Framework
versions. Maybe I need to do a manual uninstall, but don't know how to go
about it. I am afraid of deleting files (including registry entries) needed
by other programs. Anybody know where I can find some detailed instructions?
I am running Windows XP Professional, sp 2.