Unable to debug in VS2003 after installing VS2005

I was unable to debug asp.net project in VS2003 today,because I installed VS2005 Beta.

There is a error message that I got

************************
Microsoft Development Environment
************************
Error while trying to run project: Unable to start debugging on the web
server.

Click Help for more information.
************************
OK   Help  

Why?

Think about it a while, installing VS2005 should configure IIS to use the V2.0
net Framework, so the VS2003 can't debug in the new version.

Then I have a try, uninstall the 2.0 mappings from IIS using aspnet_regiis.exe -u
in /windws/Microsoft.net/Framework/v2.0.** folder,
after this configure IIS to use 1.1 net Framework using aspnet_regiis.exe -i
in /windws/Microsoft.net/Framework/v1.0.** folder.

This works great

 , but when I want to debug VS2005 project,I have to do the same
thing in reverse.