You can configure communication ports as described in the previous section or as described in "Serial Subkey Entries in the Services Subkey" in Chapter 14, "Registry Value Entries." You might also need to delete one or more COM ports, which you can only do by deleting the related Registry information in the DeviceMap and Services areas of the Registry. To delete entries in the DeviceMap subkey, you must be logged on as a member of the Administrators group.
HKEY_LOCAL_MACHINE\Hardware\DeviceMap\SerialComm
The value entries in this subkey are used to determine all the communication ports available on the system. The values are of the form Serialyyy=COMx, where COMx can be COM1 to COM256, and Serialyyy can be from Serial0 through any large positive number such as Serial15000.
You can identify the value entry you want to delete based on the list that appears when you choose the Ports icon in Control Panel.
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
\Serial\Parameters\Serialyyy
If you do not delete the related Services subkey for Serialyyy, the COMx port continues to appear in the Ports list in Control Panel each time the system starts, even though there is no related DeviceMap subkey.