Today I formatted my Mac Pro, and I always run into a problem with my iTunes Library. I like to keep it off my system drive as it is a small 120gb ssd drive. When I try to tell set my iTunes folder to the other hard drive it does not recognize the library and has no songs. This is made even more frustrating when Apple decides to keep updating the folder structure (9.2 in this case). So here is how to fix your iTunes library.
1. Copy the files and folders inside the iTunes folder to the system drive and click on replace all.
2. Click on the iTunes Library file.
3. Now iTunes should open up and have your library intact and will probably update it to the new format.
4.Copy it back to the location you wish to have it at.
5.Press option (shift on pc) while opening iTunes and it will ask you which iTunes library you want to load.
6.Click Choose Library…
7.Find the iTunes folder you want and click on the iTunes Library file.
8.Now it should be working fine, you can delete the old folder!