Windows movie maker finalization process?

I loaded and inserted a video into windows movie maker, the only thing I did was add music in the specified slot so it would be there with the video and I could finalize it and the video and added audio would be there. I finalized the product, but only the audio came out. There was audio already on the video, I just added music with it. Both the added audio and the audio already on the video was there, but there was no video at all. The audio played fine, but the final product had no video. Did I do something wrong? Is there a special thing I have to do to put both audio and video in the final product?

Thanks

Yes I opened it in 3 different programs all of which should support audio. None of them have video, but all of them have the audio added in movie maker, and the audio originally on the video.