How do I play videos on my motorola droid?

I’ve downloaded videos to my droid but they aren’t working. They’re movies and they are mpeg 4 files. Even the videos I didn’t download through itunes aren’t working. Can someone help me figure out how to play videos?

Here is a article on video converters.Maybe,you can get some information. http://www.squidoo.com/convert-video-to-mac
Of course,you can download them here. http://www.best-video-converter.net/