I have deleted the application in IIS 3.5.1 sp1, removed the registry key HKEY_CURRENT_USER\Software\ESRI\ArcGIS Silverlight Viewer. I have 32bit system windows XP. All my MIME types (.xap and .xaml) are there in IIS. When I install, the prequisites check list verifies all succeeded as well. I believe it could be a permissions issue? The last event viewer log gave me this error:
Event Type: Error Event Source: ASP.NET 2.0.50727.0 Event Category: None Event ID: 1084 Date: 7/12/2012 Time: 2:39:39 PM User: N/A Computer: CITY-0294 Description: aspnet_wp.exe could not be started. The error code for the failure is 80004005. This error can be caused when the worker process account has insufficient rights to read the .NET Framework files. Please ensure that the .NET Framework is correctly installed and that the ACLs on the installation directory allow access to the configured account.
However I'm not familiar with ASP.net permissions and config files for that. I didn't think it was going to be this complicated to start up, is there something else I am missing that I should attempt first before trying to fix ASP.NET stuff?