I did a little searching and confirmed that .Net 2.0 can't be uninstalled on Vista and probably Windows 7 as well.
Did you try installing .Net 2.0 on top of itself? There's also a 32 bit and a 64 bit version. You could try both of those to see if they would.
There's also this link on repairing .Net 2.0 on Vista. May or may not do anything for you.
http://blogs.msdn.com/b/astebner/archive/2007/03/26/how-to-repair-the-net-framework-2-0-and-3-0-on-windows-vista.aspx
It's possible I may be overcomplicating the solution as well. I do not think you are the only person to have had that issue, but I can't remember what was done to fix it.