Window CE and Windows Mobile offer a limited number of serial ports (COM0-COM9) by default, and some of them can be already used by other devices. In case of shortage of virtual serial ports you may free existing ones and create virtual serial ports instead to be able to use them in your own scenario. To free existing ports, please, click icon in Windows CE or Windows Mobile Pocket PC:
In Windows Mobile Smartphone, please, select occupied port you want to disable, click left soft key and then "3" button:
Please, note that ports you make free with VSPD Mobile preserve the state even after system reboot.