Trouble playing videos

I am trying to compose a study using DirectRT that plays videos I have made (.wmv format). I have a Dell laptop which runs Vista. When I try to run your "video sample" (excel file attached here), however, it doesn't even play those videos. When I run the test, it plays through, shows the text, and allows me to press a button as if I am responding to seeing the videos on the screen...but the videos never come up, the screen is just black. Do you have any idea why this is? Is Vista the problem? Is there anything I can do?