Moving my iTunes music to another disk (out of disk on the C driv

Copy iTunes folder to your external hard drive
To copy all the items in your iTunes library (including the iTunes Library file that holds all your playlists, playcounts, ratings, and other data) to your external hard drive, follow these steps:

Quit iTunes.
Locate your external hard drive.
Mac: On the desktop or Finder sidebar.
Windows: In My Computer
Locate your iTunes folder:
By default, the iTunes folder is located in:
Mac OS X: /Users/username/Music
Windows XP: \Documents and Settings\username\My Documents\My Music\
Windows Vista or Windows 7: \Users\username\My Music\
If the iTunes folder is not in the default location listed above then you can find where the iTunes folder is located by following these instructions:

Open your iTunes Preferences:
Mac: Choose iTunes > Preferences.
Windows: Choose Edit > Preferences.
Click Advanced.
The location of your iTunes folder will be listed in iTunes Media folder location box, as pictured below.


Drag the iTunes folder to your external hard drive. This can take a while if you have a lot of items.


When the transfer is complete, your iTunes Library will have been successfully copied to your external hard drive.

Before iTunes 9, there used to be a "iTunes Music" folder that contained all of your music, apps & videos. With the newest version of iTunes, this folder has been changed to "iTunes Media" on new installations. This new folder structure makes much more sense than before, because iTunes is definitely much more than just music now.

However, if you already had iTunes installed before and simply upgraded to the latest version, iTunes will not automatically change the folder structure for you (I guess as to not move an existing user's files around without telling them). You'd have to take a few steps to keep yourself updated.

First, open iTunes, then go to "File > Library > Organize Library". You will be prompted if you want to change to the new iTunes folder structure. However, this will not change your top level folder, "iTunes Music". To do that, leave iTunes running, and simply go to your iTunes Music folder and rename it iTunes Media.

Most of the time this will work fine, because iTunes will detect that there's been a folder change and work accordingly. In case that iTunes didn't catch the folder change, go to "Options > Advanced" and change the location of the iTunes Media library folder manually.