1.Go to your 'My Music' folder - it's inside your 'My Documents' folder.
2. Look for a folder called iTunes, and look inside to see if there are music tracks.
3. If you see tracks, launch iTunes and reduce the window size. Now go back to to 'My music' and drag the iTunes folder into the iTunes Window. Drop it on the 'Library' icon at top left of the panel marked 'Source'
You'll see all your tracks appear, but you'll have lost your play-lists.