Das Werkstatt

[PROBLEM]
After installing some extra COM ports (e.g. after attaching an Edgeport), their assigned numbers are not the ones you wanted.
(e.g. COM3 is assigned as COM11)

[SOLUTION]
Open:
ControlPanel -> System -> Hardware(tab) -> DeviceManager

There right-click on the to-be-changed COM entry and select
Properties -> PortSettings(tab) -> Advanced

...and there you can tell the system which COM port this 'should' be

Here is another approach, that lists all hidden devices in the device manager, so you can delete and re-install them:
Showing hidden devices