I found this article very helpful when troubleshooting an issue with my vanilla Windows 2003 server. Earlier this week, I deployed an application that used Silverlight. The app worked fine in my development environment and my Windows 2008 test environment. After I deployed it to my 2003 IIS6 sandbox server, I noticed all my Silverlight controls weren’t appearing in the browser. You could right click on them and get the Silverlight context menu, but the controls themselves were not loaded.
After googling around a bit, I found this article extremely useful. MIME Types… My server had nothing on it but IIS and Asp.Net. Naturally, Silverlight components were not setup in IIS. So this was a super easy fix by just adding the three new MIME types to the IIS Properties dialog. Check out the link for more details.