He's asking why he his computer is giving him an error message about all COM ports being in use. Unfortunately section of the forum is about networking, and COM ports aren't networking, they're more general computing.
I'd check and make sure you dont' have any modem software running and that you're trying to connect using the correct COM port. I like puTTY as a client, it's free and it works.
If the above doesn't work to get connected to your 1700, then I'd recommend posting the question in one of the other sections of the forum related to either your computer model or your operating system. This isn't a networking question, even though you're trying to get connected to a network device :-)