Try searching your hdd for them. From your desktop go to Start>Search>All Files and Folders, and search for them by title or file type(mp3). They should all be in the same place. The default location of your saved folder is C:\Documents and Settings\"your account name"\Shared.
If you can't find them do a virus scan. Some viruses will erase your library. Try using
AVG Anti-Virus Free Edition, it catches most of them. Also see:
WARNING: Viruses on network you should be aware of!
Unless your os is Vista, then try wondering why's advice here:
http://www.gnutellaforums.com/genera...tml#post279522