Lost library

I have a classic Ipod which lost it's music. (Synced with empty Itunes?) The music was in hidden files on PC which I copied to Itunes "media" and they were also deleted. I had already copied these files to a separate hard drive. There is 16GB of music files but how do I convert or send them into itunes? I cannot open the files but 16gb means there is a lot of data in there?

via iLounge Forums http://forums.ilounge.com/itunes-related-mac-pc-applications/278290-lost-library.html