Whenever a new USB serial device is plugged into a PC, Windows will assign the device a new, unique COM Port number. This will even happen if the same device is plugged into a different USB port.
If you are prototyping or experimenting with different USB devices, this can cause the COM Port numbers to become quite large over time. Although there is no reduced performance associated with high COM Port numbers, you may wish to have a specific COM Port number assigned to a specific interface board.
This guide shows instructions on how to remove and change COM Port Assignments in Windows 7. Because the process requires you to enter the Device Manager, caution is advised.
Show all Com Port Assignments
*This should automatically open the Device Manager for you.
To remove an old COM Port
*You will want to reboot your PC after removing the unused COM Ports.
To change COM Port assignments
*After making this change, reboot your computer to ensure that the COM Port has been properly assigned.