If you had installed IIS on Windows XP Professional machine afterwards you had already installed Visual Studio 2003/2005 or .NET Framework 1.x/2.x you will probably encounter error “Failed to access IIS metabase” while trying to run your web app in IIS (http://localhost/appname). The solution that worked for me in that case was executing following command line: aspnet_regiis -i. This utility is known as ASP.NET IIS Registration Tool. Off course, before running this command line you’ll have to make sure that you’re in the right folder which is, in the case of ASP.NET 2.0, C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727. This will properly register ASP.NET ISAPI in IIS. More on this can be found here.