I am using Windows NT since Vs3.1 in 1994 and IIS since 1.0 in 1996. So I have a bit experience with these systems and still use mostly Microsoft technologies.
IIS Troubleshooting tools:
- Process Monitor - Finding out about failing file access
- Test-WebSite - PowerShell scripts for testing an IIS web site and suggesting fixes
When I make money it is usually as a .NET developer.