You can manually edit the file C:\Program Files\DeskNow\conf\server.xml (or /var/desknowdata/server.xml in Linux/Unix) and comment out (or entirely remove) the element under the line <!-- This connector is for normal HTTP connections -->

To comment out the section, simply add !-- at the beginning of the opening tag, and -- at the end, like this:

<!-- This connector is for normal HTTP connections -->
    <!--Connector className="org.apache.coyote.tomcat4.CoyoteConnector" port="80" minProcessors="5" maxProcessors="75"
               enableLookups="true" redirectPort="4443"
               acceptCount="100" debug="0" connectionTimeout="20000"
               useURIValidationHack="false" disableUploadTimeout="true" /-->

You then need to restart DeskNow.