If you haven't got Vista, this might do it for you. I found this 'FIX' on the net...
"I pulled my hair out for a few days with this same problem recently, only on an XP. No media player I had installed would "see" either of my mp3 players. Turned out to be the MS Application Compatibility Client Library (whatever that is)
The fix. Uninstall WMP and then reinstall it. This should reinstall the Application Compatibility Client Library which apparently is needed for ANY media player to "see" mp3 players in Windows.
Note: I reinstalled WMP twice before it actually worked, which is why it took a few days to finally figure it out."