How to serve unknown file types from IIS 7
Solution 1:
You can add an universal MIME type by using the extension "*" and the type "application/octet-stream": http://support.microsoft.com/kb/326965
Solution 2:
Instead of going through the MMC like the kb article suggests, you can also just create a Web.config file in the directory, with the following content:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<staticContent>
<mimeMap fileExtension=".*" mimeType="application/octet-stream" />
</staticContent>
</system.webServer>
</configuration>