My downloaded files seem to be LimeWire format documents (rather than MP3, JPEG etc) which will not open or de-compress. How do I convert these files to their original formats?

All I had to do is double click the file and then it would be opend by iTunes, Pictureviewer, Quicktime, ... and everything worked fine!

Just rename the file - click on the icon's filename, and edit it - usually all you need to do is just add the extension on the end (i.e. .mp3 .mpeg, etc) - THEN you should be able to reclaim the file.

HTH,