You are not able to download files with certain extensions.

IIS Requires that all downloadable files have a registered mime type.  You may need to add a mime type to your website.

1)  Log Into your control panel and select your domain.



2)  Click On Web Directories



3)  Click the Mime Types link







4)  Click Add New Mime Type.







5)  Type in the extension you want to add, select Custom, and then type in the Mime Type (You may have to use Google to find the mime type out).  Then click OK..