- Mount the disk drive to you computer. In the root directory create a folder called "Media"
- Inside that folder make bunch of folders called "Music" "Music Videos" "Videos" "Ringtones" "Alarms" etc.
The phone will auto detect those folders. In particular it will notice the Music folder, the Alarms folder and the Ringtones folder.
In the built in music app, all the stuff in the "Music" folder will be there.
In the gallery app, there will be a list of the folder names you created such as "Music Videos" which is a good place to keep downloaded youtube videos.
There will also be a category near the top of the "gallary" application that says "all videos" or "all pictures" which will show you every video or every picture that is anywhere on your SD card.