Trying to get my new 2011 mini to connect with my HD. It recognizes it's there, but can't get it to work in iTunes and access my music. Little help please 
I assume the HD is an external USB or FireWire drive that you can browse and see your music files in the Mac Finder.
When you change the iTunes library location in Edit > Preferences > Advanced > iTunes Media Folder Location, that will be the location that
newly imported or ripped music will be organized and stored in,
but the iTunes database files located in
/Users/username/Music/iTunes on your home drive don't have that library information about your
existing external files.
If you want to preserve previous information like playlists, ratings, artwork or other information that may have been stored in the previous iTunes database files, you would want to copy the database files from the previous computer (iTunes Library, iTunes Library.xml, iTunes Library Extras and iTunes Library Genius) and overwrite the files on the new computer in
/Users/username/Music/iTunes.
That alone should make all of the music on the external drive show up in iTunes if your external drive location is the same as the previous installation. If you no longer have those files, you will need to run File > Library > Organize Library > Consolidate files. That should do it, but if it does not, you might have to drag all of the folders from the external drive library into iTunes. If you end up with duplicate songs, you can hold down the shift key and select File > Display Exact Duplicates and delete them.
Normally though, you should only end up with duplicates if you had the library stored originally on your internal (or another external drive) and are trying to move them to a new external drive. In that case, consolidating would copy the files to the new library drive location and you would end up with duplicate tunes.
Also if you have any existing DRM protected files purchased from iTunes, you would need to Deauthorize them on the other computer (Store > Deauthorize This Computer).
Hope that's not too confusing. It goes without saying that it is always a good idea to keep a current backup of the library files and the music files.
Steve
