Most devices of this type require a separate set of drivers in Windows to be visible to user applications as a Com port device. Sometimes these drivers are installed by default and sometimes not. In particular if you are using the device with the Window's included drivers then you are going to normally end up with the OS loading the drivers applicable to the most common usage model of the particular device. If you are already loading device specific drivers from the vendor then investigate if they have the virtual Com port drivers available separately. Another thing to look for is some special check off box in their device's Install/Setup program that would tell the installer to include the virtual Com port capabilities in the installation.

Michael Karas