I do not have iTunes configured to copy music files to my iTunes library. (I don’t need another copy of my files, which are on a network drive.)
I found stories on the net, saying to delete the content of "iTunes Library.itl" and to edit "iTunes Music Library.xml" to reflect the new location. The story is that iTunes would detect the corrupt .itl file and rebuild from the xml file. I tried it. It didn’t.
My new ‘protocol’ is to make all of my music accessible via M:\, where I have subdirectories named mp3 (where my music lives) and books (where audio books live). If I move the library, I have to move M: to point to the same structure. In the simple case, I do this with a new drive mapping. In the more complex case (suppose the share points to \foo\bar and mp3 and books live in bar) I would then map the share to a different letter (e.g. N:) and then use subst (e.g. "subst M: N:\foo\bar").