My old computer hard drive crashed, but luckily I had Crashplan, and I was able to restore all my PC files on the new computer. When I got to iTunes, I had the exlamation points also, every song, all 12,000 plus of them.
Whenever I had added music on my old computer, I always went to Library, and click Consolidate after adding, as I added music from iTunes, other websites, and Cd's.
I wanted the songs on my new computer, on my larger 2nd Hard Disk (D:) on the new PC.
So I copyied all my iTunes files/folders to a new folder D:\itunes. (this included the library file, artwork etc., everything, plus the iTunes folder that I could see had all the album songs.
When I opened iTunes, I went to preferences, Advanced, and directed iTunes too look at D:\itunes
When I opened iTunes, I still had the exclamation points on every song. I clicked the first song and got the message "could not find original...".
I chose LOCATE, and clicked through to the iTunes folder to that exact song, and clicked OPEN (or OK).
Then iTuens autmatically prompted to locate the other missing files/songs. I clicked YES.
iTunes sort of froze up, but it was doing something; so I just let it run. I had over 12,000 songs, and it took about 20-30 minutes; then a message popped up "iTunes was able to locate all the missing files".
Yea, they all work, all my artwork, and playlists were there.
I closed iTuens, and re-opened, and it did another routine automatically, took a couple minutes; not sure what this did, but did not affect anything. I closed and reopened again, and all is good.
I was really worried as I tried other methods, but this worked great. Glad I had Crashplan to backup all my files.
Of note: I prefer Crashplan as opposed to Carbonite, as Carbonite says "unlimited", but it does limit the individual file size; whereas Crashplan backs up all files you choose, regardless of the file size.I think I will look at the iCloud backup for iTunes, as I have so many songs, I think it would be worth it as a secondary backup.