Help - i need help syncing 2 libraries

Hey everyone and anyone. I have a problem...I have a Macbook Pro and a G5 powermac. So... therefore I have 2 itunes libraries. When I got my G5 recently for christmas I decided to move my entire itunes library to a hard drive to free up space on my MBP I then moved all of that onto my G5 to make it my main multimedia computer. But because I'm an idiot I have now added songs to both Macs at different times and I'm in a complete mess. When I deleted my files from the MBP after moving the itunes library to my hard drive I noticed that on my MBP's itunes library all of the track names remained in the library but when I press on them they dont work and a exclaimation mark appears presumably telling me the track isnt available or accessable. So i undersand this. BUT now I have no idea what I have and havnt imported and dont want to loose any of the tracks. All of the tracks work on the G5 but how do I now find the tracks on my MBP that I need to move?