Before proceeding, please read the warnings associated with storing your music and video files.
Here are instructions on how to move your iTunes library for Windows.
If you have a Mac, follow these instructions on how to move your iTunes library for Mac.
If you would like to remove the music from your H: drive, go to "My Computer," locate your personal music folders on your H: drive, and delete them.
For additional iTunes information, see the iTunes Resources help page.