After browsing the discussion base for some hours.... it seems that I have found at least someone with a similar issue than I have.... As Eddie explained, he had (and wanted to keep) the library on the internal HD and wanted to move all his sound files to a new Ext.HD, without loosing all the information of his old library. He managed to do that with the tipps and tricks of Limnos.
Now, my issue is similar: my iTunes library is on my old powerbook and I want to move it to my account on our new iMac (one iMac 27 late 2012, two users). My sound files are partially on the old powerbook and mainly on the external HD (the one which I want to continue to use with the iMac). Although I have read the article on Apple's support page on how to move an iTunes library.... I doubt that I want to have my library managed automatically by iTunes, because I want to keep track myself on the relevant sound files I added to the library.
So... I guess I want to first move the sound files from my old powerbook to the external HD (so that all sound files are on the ext.HD => now the same set-up as Eddie uses, I understand), however, iTunes should continue to recognise the place were they are stored (new place!) and also the relevant sound information (ratings, etc.). I think that this is the complicated part. As I understood Limnos tipp correctly, I should - after I moved the sound files (by dragging and dropping) to the external HD - open iTunes and go to the first sound entry with an "!" and then show iTunes where the original file (now) is, i.e. on the external HD. iTunes then will apply this logic to all other files with "!" and should fix this issue by itself..... if I understood correctly, this is it, right?
Secondly, I then want to move the existing iTunes library file from the powerbook to the new iMac. Of course also with this step, iTunes should of course not lose track of the places and the relevant information. Is the assumption right that I then should only repeat the steps as described above and when opening iTunes on the new iMac (perhaps pointing the new iTunes app to the relevant iTunes library which I now copied to the new iMac), just open the first file with an "!" and then browse to the relevant original file (on the external HD), and then..... miracle..... iTunes should fix all the broken links by itself again.
Do you think this assumption would be right and could be a solution to my issue?
Although the above discussion is already 6 months old..... I would be gratefull for an answer
Thanks Mike