Make sure the current driver is installed. After plugging in your receiver, you should be able to determine the com port of your device by checking Ports under the Device Manager or scanning the com ports from the GPSInfo program.
Since the GPSInfo utility has several versions, one of them has com ports only listed up to COM19. If that is the case, you can download the other version here: (http://www.usglobalsat.com/GPSinfo.zip
). This will allow you to select a com port further than COM19.