- Stop the IIS Admin service and any services that depend on it.
- Open C:\WINDOWS\system32\inetsrv\MetaBase.xml in notepad or your favorite XML Editor.
- Delete the line that reads Enable32BitAppOnWin64='TRUE'
- Start IIS via Windows | Start | Run | iisreset
On a Windows 2003 64bit machine with both .NET Framework 1.1 and 2.0 installed, you are tying to configure a website on IIS, but you are unable to find the tab to specify ASP.NET settings.
SUMMARY of TROUBLESHOOTING
Researched turned out this being a bug that is closed as "won't fix".
Click here for the link to blog article on MSDN Blog.