If you are trying to debug the ASP.NET application with Visual Studio 2005 (VS 2005) and Windows XP, and getting the following message,

Unable to start debugging on the web server. Debugging failed because integrated Windows authentication is not enabled. Please see the help for assistance.

Then do the following settings under IIS.

• Open control panel–>Administrative tools–>Internet Information Services
• In IIS, select the website in left tab, right click ‘Default Website’ under it and click on properties.
• Under the ‘Directory Security’ tab, click on Edit under ‘anonymous access and authentication control’
• Check on ‘Enable Integrated Windows Authentication’.

Prior to this ensure, ASP.NET and IIS is mapped. If not, goto VS.NET command prompt and type the following command

aspnet_regiis –i

Happy debugging