If you are using a Serial-USB adapter to connect to the HD15 connector, the Wavecom Modem will simply appear as a COM port, as mapped by your Serial-USB adapter. No drivers (other than those for your USB-Serial converter) are required. Any of the Generic Modem profiles from Windows will work (more or less) with the Wavecom Modem.
You only need a specific USB driver if you are connecting directly to the Fastrack via USB (i.e. using an IESM card with USB). In this case, the USB drivers are available from the Wavecom Products page on the web site. Select your device from the list, then look under the Downloads tab.
Note that you will need to create a Developer login to access the downloads. Follow the instructions from the Create an Account button at the top of the page. The Developer Login is different to the Forum Login…
I think the problem is that you dont have installed the driver for the USB-Serial cable. To be sure just plug the cable without the Wavecom module and see if you get the same result. If you get the same result the problem is that your USB-Serial cable adapter needs a driver to work properly on Windows, the driver should be on the cable´s box or in the manufacter web page.