29,000 songs frozen

I had a new internal hard drive installed in my iMac (10.6.8) yesterday. I keep 29,000 iTune songs
on an external drive. To my relief, the songs played fine when I powered up the new drive. However, I noticed
this morning I could only upload songs from bands that had no previous file (or songs) in my library, and that
I could no longer alter any of my existing song's "info."
By going into a specific performer's iTunes folder and going to GET INFO and adding "Admin" as a
recognized user, I was allowed to import a new CD by that performer. By doing the same to a specific
album folder, I was able to alter the existing songs on that specific album. So, while all the albums
on the external drive are playable, no existing song data can be altered, nor can I add any music
by existing artists without altering their existing artist folder first. I can't alter existing songs without altering
individual album folders.

How can I get everything to jibe again...and what went wrong? Can I somehow use the
"Get Info" user settings to change 6,500 folders at once? How can I regain full control over my library
on the external?

It's conceivable some "users" were deleted during the hard drive crossover, but it seems any
names that conceivably could have been keepers of the iTunes library are still present.