Hi fella!
Ok, we'll start with the simple things first. It's not in the Recycle Bin is it?, the icon is usually on the desktop.
If you're using Windows XP ....
Open up My Computer and click :
C: > Documents & Settings > [name] > My Documents
are they in there? Did she recall deleting them or moving them?
To do a search,
Click Start > Search and type in *.mp3 this will do a search for all mp3 files. The results will show all MP3's on the system and may give you more clues.
It may be just a case of the files being moved by accident.
If they have been deleted on purpose, it's not so simple I'm afraid....
Phil