Or, if you do not want to modify the system configuration file, you can add the following lines to this section in your web.config:
<remove fileExtension=".mdb" />
<add fileExtension=".mdb" allowed="true"/>
For example, your Web.config should look like this:
<configuration>
<system.webServer>
<security>
<requestFiltering>
<fileExtensions allowUnlisted="true" >
<remove fileExtension=".mdb" />
<add fileExtension=".mdb" allowed="true"/>
</fileExtensions>
</requestFiltering>
</security>
</system.webServer>
</configuration>
. http://www.adamwlewis.com/articles/iis-7-not-serving-files-4047-error.