This error occurs when another application has already been assigned to the communication port ActiveHome is trying to use. Check your available communication ports in Windows Device Manager (START | SETTINGS | CONTROL PANEL | SYSTEM | DEVICE MANAGER). Click on the plus (+) sign next to PORTS COM & LPT. Make note of the ports listed here. (Note: If your COM port settings were changed from the defaults, they may have to be reset.) Next, open ActiveHome. Under CONFIGURATION | PREFERENCES, the available comports are displayed. Take note of the ports shown here. Then, CUSTOM UNINSTALL ActiveHome using ADD/REMOVE PROGRAMS in CONTROL PANEL. Select all files for deletion. Reinstall ActiveHome. When prompted, select the COM port that Device Manager and ActiveHome have both recognized as available.