How do I get iTunes to recognize all songs in music folder?

My wife has had an iPod for years. I recently purchased my own. To get my music collection started, I hooked it up to her computer and it synced all her songs from iTunes to my iPod. Then I hooked my iPod up to my computer and all the songs were transferred from my iPod to my iTunes. From there, I deleted the songs I didn't like and added many more of my own. (It just so happened that there was already a backup of my wife's songs on my computer - think this may be contributing to my problem)
Then I recently moved my library to a different hard drive. The next time I syned my iPod, it said that there were over 500 songs that could not be found. The only way to get the songs to show up is to manually go into my wife's backup folder on my computer, copy the song to my music folder, and then either 1)double click the song in windows explorer, which starts it playing in iTunes and adds it to the iTunes library, but then I have to delete the identical song in iTunes that won't play, or 2) try to play the song in iTunes and manually direct it to the location of the song. I have accepted the fact that I will have to manually move all the songs from my wife's backup to my music folder, but isn't there a way to get iTunes to go through my music folder and recognize all the songs without having to play each one?

5th gen iPod with iTunes 7.0.0.70 Windows 2000