This thread pertains to the Touch, but I suppose might also be applicable to the Duet. See post 3 in the thread, and post 47 and the posts that follow it.
The procedure they describe involves doing some things that are a bit out of the ordinary. You have to log on to the Squeezebox via what is known as SSH, as opposed to http, ftp, etc.
The following paragraph from this page indicates how to do that, at least with the Touch:
Enable ssh by navigating to Settings->Advanced->Remote Login. After checking the checkbox for enabling remote login, there will be a help message that tells you the IP address of the controller. Note this address.The user id, if it is not automatically entered, apparently is "root."
So if your computer runs Mac OS X or Linux, you can simply follow these instructions, and then the instructions in post 3 of the thread I linked to earlier (noting that one of the entries in post 3 was corrected in one of the later posts following post 47).
If your computer uses Windows XP or Vista or 7, you will need to install "SSH client software." See this link, which references the Putty SSH client program.
The Squeezebox makers certainly haven't made this easy!
BTW, I don't own a Squeezebox, so my ability to further clarify any of this will be limited. Hopefully it will make sense to you.