Windows Movie Maker

I used to use Windows XP with no issue at all. I have just bought a new
laptop with Vista home premium and now, whenever I try to save a movie after
I have successfully edited it with transitions, effects, text and music
overlay onto the computer, it works for about 180mb then stops and turns off
the whole computer. When I turn it back on I find that only a short (approx
180mb) part of the movie has been saved. I am at a complete
loss.............HELP!!!!!!