Hi! I am currently making a video and although everything looks fine on windows movie maker when I export the video a black border appears around it. I have tried exporting in both aspect ratios but it looks exactly the same! I had even used clips in this video in a different one which did not have this problem so I am fairly certain it's not the clips themselves?  Can anyone help me out because this is extremely annoying,

Thanks!!

(heres a pic of what I mean)

Looks pretty average

weird black border