How do I get my Itunes library back?

Hi there, I have been having mucho problems with Itunes and instead of removing and reinstalling (frightened to do that in case I lost my songs!) I clicked the Repair on in Add/Remove programs. Now when I open up Itunes it is empty - my library, playlists everything has gone!! I tried doing a System Restore to an earlier date but is still the same. Can anyone help please? Thanks!