What format are your videos in?

My videos are in H.264.

I found that H.264 to be the best format for the videos. The easiest way to play this format is with QucikTime. Available at http://www.apple.com/quicktime If you're using Windows and want to continue using Windows Meida Player, you'll need to download a "codec" for H.264.

For Windows I recommend the Combined Community Codec Pack. It not only has H.264 but most major codecs that aren't included with Windows.