Powerpoint is based on the concept of slides. It is this concept that makes powerpoint simple, but it also constrains the scope of what can be done tih powerpoint. And unlike presentation tools such as flash, Powerpoint cannot keep an object accross slides.
You will be able to open a video, and play it on one slide but you will not be able to play the video continuously accross slides. Everytime you go to a new slide The video will start from the begining, becoz PP loads it at as a new object every time.
Powerpoint does not perform automated multiple operations at the same time. i.e., you cannot automatically animate text while the video is playing. You might be able to do it using a manual click. But again if you are going to do something like that the entire presentation must be done with only ONE slide.
You must consider some other software. Flash does these kind of stuff well. Perhaps u must try it.