Thanks Chuckoir!

Just to clarify, this is how things are -

Before I upgraded, I had transferred all my music to a folder on my external hard drive, and the itunes was therefore directed to that folder.

However, after I had upgraded, all the tunes had disappeared from itunes but, the songs were obviously still in the folder on the external hard drive.

Now, if I 'add files to library' from the external hard drive, will I be just adding the song titles OR, will i be transferring the actual music itself back to my mac?

Thanks again,
Mcdad