I had a bunch of problems reinstalling .net framework 1.1, it kept coming with an internal error 2908 and failing to install.  I spent a bunch of time cleaning the registry, only to find this didn't help.  I finally tracked down this article, which said to rename mscoree.dll in the Windows\System32 directory.  This worked like a charm, making the system correctly reinstall again.  So if you have problems, do this.