When you try to create a new Microsoft ASP.NET 1.1 application after you change the script mapping of the existing ASP.NET 1.1 Web application to ASP.NET 1.0 on a Microsoft Windows Server 2003-based computer, you may receive the following error message:
The Web server reported the following error when attempting to create or open the Web project located at the following URL: 'http://localhost/822319ev1'. 'HTTP/1.1 500 Internal Server Error'.
CAUSE This issue occurs because Windows Server 2003 does not allow two versions of ASP.NET to run in the same application pool.