The default movie player under Ubuntu 7.04 is Totem and this blog post describes it and how to use it best.
Read it here
When you have a file you want to play. simply double clicking on it should open Totem. If you want to play multiple files in a row, drag the files from the desktop or a file explorer into the playlist sidepane of Totem. Files will be played in the order in which they appear. If you want to change the order of play, either drag and drop the file to its new location or choose the file to be moved, then move it using the up and down arrows. If you want to shuffle or repeat the playlist, those functions are located under the Edit menu.