iTunes won't respond

I will start off by saying I don't know much about computers at all, so please bear with me. We opened our iTunes the other day to find that almost everything...which is alot, like 60ish gb...was gone. We moved the iTunes files from documents to iTunes and it seemed to work. We worked for 2 hours on redoing playlists and checking to see if everything was there when the iTunes stopped responding. We have removed the program from the computer a few times so we could re-download it from iTunes...I thought this would give us a fresh program but it comes back to the same frozen program with the partial playlists I had been redoing and is just frozen. Can anyone tell me why this is or how to try and fix it? Three of us have iPods and really love them but sometimes iTunes is the most aggravating thing on the planet!
Thanks!