I was attempting to uninstall Visual Studio Express 2005 and had a little problem.  It hadn't made any progress in a few hours!  A quick search and I found out why.  The installer expects you to have the product registered!

Quan To has the quick solution to the problem, just kill the VSE process and it finishes the install.  For c#, it was VCSExpress.exe.

This problem had to have been fixed in 2008 but you never know.  You get some cool free stuff also for reg'in your copy too so just heads up.