The project is not configured to be debugged; this error is very common when we try to debug ASP.Net web applications using Visual Studio 2005. Follow these steps to resolve this problem by applying the Integrated Windows Authentication:

Steps for Windows XP IIS 5:

1. Open run command and type inetmgr and press enter. It will open the Internet Information Services Manager.
   
   
2. Now expand the local computer name from the tree view at left side.
   
   
3. Next expand the Web Sites.
   
   
4. You will get a Default Web Site icon.
   
   
5. Now right click on it and click Properties.
   
   
6. It will show the Default Web Site Properties.
   
   
7. Select the Directory Security Tab.
   
   
8. Click the edit button of Anonymous access and authentication control, to enable the anonymous access and edit the authentication methods for this resource.
   
   
9. Now select the Integrated Windows Authentication check box to enable it.

Now you are ready with IIS enabled with Integrated Windows Authentication.

Steps for Windows Vista:

1. Go to control panel and open programs and features.
   
   
2. Then click Turn windows features on or off.
   
   
3. Now expand the Internet Information Services, then World Wide Web, and then expand Security.
   
   
4. Now select the Windows Authentication check box to enable it.

Above steps will install windows authentication mode in IIS.

To enable the Windows Authentication for default web site of IIS 7. Follow these steps:

1. Open run command and type inetmgr and press enter.
   
   
2. In the IIS manager expand the local computer and click on Default Web Site.
   
   
3. In the right side panel double click on Authentication, then right click on Windows Authentication and enable it.

If above feature of Windows Authentication is not present in your Windows Vista then you can refer the following article to debug the ASP.Net application…

Visual Studio 2005 - How to Start Debugging on the Web Server

See Also:

Visual Studio 2005 and IIS 7 configuration problems - Windows Vista 

Unable to Start Debugging on the Web Server