ASP.NET 1.1 and 2.0 installed on same machine.

I ran in to this error the other day when I installed Visual Studio 2005 on my machine and tried to debug a web project written in (.NET 1.1) and in .NET 2003 IDE.

“Unable to start debugging on the web server”

The following article was useful for checking some things.


I tried to repair .NET Framework 1.1 , adding the http://localhost to trusted sites group.

However, nothing helped me.

I then tried to go to IIS-> My Web Project node and rtclick and go to Properties window.
There, I clicked on General Tab -> Configuration button, this brought up an Application mappings window, which had .aspx resolved to 2.0 framework’s isapi dll, I changed it to point to 1.1 framework’s isapi dll and everything started working.

I hope this helps somebody there.