Can you tell me what you used to rip those cds?
If its Media Player those will be listed as a *.wma file, by default WinMX wont share those types of files for a good reason.
Windows Media Player has a nasty habit of placing personal information of the computer user into the tracks. This is usually imbedded in the track and its not wise to share them this way.
My best advise is to re rip these files using a free ripper such as CDex which you can find on our links page in the Audio section.
If you dont want to, and would rather share these files on WinMX you can go to the shared files or library page and select shared file types, there you can add your *.wma formats and they will show up fine..