Check out this software that will help you convert your own videos and put them onto your phone's memory card.

- 3GP Converter, found at http://www.nurs.or.jp/~calcium/3gpp.

- Quicktime Player, avaliable at www.apple.com/quicktime. You don't need the Pro version to make the 3gp files, but when you install it, make sure to do a CUSTOM install, and select the "QuickTime Authoring" feature. Quicktime MUST be installed on your computer; If it is not, 3GP Converter will throw an error when you try to convert a file.

More details on the procedure can be found here.