I came across an issue where WSUS and Microsoft Update kept getting an error installing .NET Framework 3.0 SP1 update on Windows XP PC.  I went to add/remove programs to uninstall .NET Framework 3.0 but there was no button to uninstall it. 

I thought that something was goofed up, so I came across a .NET cleanup tool that automated a manual uninstall of all .NET versions.  After this was done, I tried Microsoft update again and it still failed during installation of .NET 3.0 SP1. 

I ran the cleanup tool again and tried manually installing each version using the direct downloads from Microsoft and installation still failed. [more]

After some more researching, I found mention that .NET 3.5 SP1 would try to install .NET 3.0 if it was not installed.  The installation of .NET 3.5 SP1 worked and I saw that .NET 3.0 SP2 was actually packaged in with it. 

I ran Microsoft Update again and verified that there were no longer any updates needed by the PC.