I'll just use the version I've started E-Mailing around.
You'll need to try and delete 2 things.
Open a finder window (Double click on your HD).
Now open the folder called Users. (If your in list view it will be at the
bottom if not you can look around and find it. It has a picture of the torso
and head on it.)
Next open your file in there. It should be obvious which folder is yours. If
it isn't E-Mail me and I'll tell you exactly how to figure out which one is
yours.
Now when your in your folder (This is called your Home folder) open the
folder called Documents.
In there, Delete the file called "iTunes Music Library(1)" or it will be
called something similar to that. *Warning* DO NOT DELETE ANY FOLDERS IN
HERE! JUST THE FILE OR YOU MAY END UP LOSING YOUR ACTUAL MUSIC! *Warning
end*
Now go back you your Home folder.
Open Library.
Open Preferences.
Now you will need to delete a file called "com.apple.iTunes.plist" You may
want to be careful because if you delete any other files you will lose the
preferences for whatever application you deleted the preferences for.
Restart iTunes.
It should ask you the questions as if you just started it for the first
time. Answer them and let it scan your Hard Drive for your music files
again. If it doesn't work or you need more help E-Mail me again. Also go up
to your Apple Menu and select System Preferences. When your in there select
Software Update. Now click "Update Now". If anything needs updating I'd
suggest you leave it downloading overnight.