I am somewhat new to this but I can tell you my experience.
I use Realplayer as my universal media player. As a result, I clicked on options under the tool tab in limewire and turned off the limewire media player. Restarted my computer so that the change would take effect.

Now, when I download and click on the downloaded file, realplayer automatically opens the file and plays it. It then adds the file to your realplayer library. If i want to save files on CD I use realplayers "Playlist" set up and organize them and then download them to cd. You can then delete the downloaded file from the download "saved file" list in limewire to save space on your computer.

BUT!!!!!! when you delete the file in limewire "Saved Files" it is no longer available to your media player. The CD you made is of course fine. But although you will see the file listed in your media player when you go to play it after deleting it from limewire, it no longer exists.

I hope this is of some help. There may be other ways of handling this which are simpler or better and if so I hope that someone will let us know. But meanwhile I have found this works.
Hope this helps you!!