This can be found in the Control Panel>System>Device Manager
The Tcl libraries only allow COM1 through COM9 to be used. Your serial connection must be on one of those ports. That can be changed in the Windows Control Panel.
Control Panel> System> Hardware> Device Manager> Ports> Port Settings> Advanced
This will be shown if the port you were using last time the program was run is no longer available. You must reselect a Port using the Option Menu to reestablish communication with the ARMmite or ARMexpress.
See Connect USB
Have Fun!!