Don't do this with .Net 2.0 Beta 1 !
Well hopefully this will help somebody to avoid the same mistake.
Like many others I rushed on the new VS 2005 Express Beta 1. I installed on a machine with a previous version of .Net 1.1.
Thankfully this is not my main production PC. I run then in a series of small troubles, but like a coming storm, it gets to a point where I was unable to start any debugging session with a VS 2003 project.
I registered again the aspnet isapi dll under the .Net 1.1 folder but no hope, still an error (0x8013134b error code) when I was trying to debug the application.
The only cure I found was to remove completely .Net 2.0 from this machine. So obviously something goes wrong with different frameworks installed.
OK it's a Beta, but hey when you have a new toy, you want to play.