This isnt really a programming forum, but in order to answer your question, some details will need to be clarified.
First off, does the port actually work? Can you use hyperterm to talk to an external modem?
The real question is What are you doing to talk to the port. If i had to guess, you are writing 16 bit code which using ancient APIs to talk to the ports.
Check out this link: http://msdn.microsoft.com/library/de...sdn_serial.asp
See where you are diverging. If there is a problem about a specific API function, we'll need some sample code to assist further.