Registering MIME Types in IIS

Recently a new extension (Office 2008 - .pptx) could not be accessed via IIS. It showed a 404 (file does not exist error). Basically, the MIME type for the new Office Extensions do not exist in IIS.

Instructions for adding the extension:

1. Get to the IIS Manager
   
2. Right click on the Server and select “Properties” to modify the global behavior, or 'Websites' or any specific website to edit just that one.
   
3. Select “HTTP Headers” (or skip straight to 4)
   
4. Select “Mime Types”
   
5. Enter a new extension (no leading period is required) and the appropriate mime type. Repeat as needed for each extension.
   
6. Click “OK” to close all the dialogs
   
7. Restart IIS i necessary
   

 Try this method if a file fails to show even though you are certain it exists.