Close a modem opened port on 2003

Hi,
I have a windows 2003 server with exchange running on it and also a Fax
server application(GFI FaxMaker), for some reason sometimes after a modem
communication the communication port doesn't close properly and the modem
status stays at disconnected. If I restart the modem and restart the
application, I get an error saying that the modem can't initialize since the
COM Port is already in use. My question is, how can I close a COM port in
windows without rebooting my server? I try to avoid downtime for my exchange
users during the day and at the same time I don't want to wait in the evening
to use my fax.

Tell me if you need more details.

Regards