Default Documents in IIS 7

<system.webServer>
    <defaultDocument>
      <files>
        <clear/>
        <add value="~/Default.htm"/>
      </files>
    </defaultDocument>
<system.webServer>

Add mime types with IIS7

<configuration>
    <system.webServer>
        <staticContent>
            <mimeMap fileExtension=".mp4" mimeType="video/mp4" />
        </staticContent>
    </system.webServer>
</configuration>