Finished AVI is too small to see

I am converting avi videos to .mov videos. As I was doing this, I noticed that some of the videos were too small (dimension-wise) to be seen.

So I went back into the original avi and their small too. This has also happened to a couple mov files I have.

My biggest problem is, I didn’t edit or convert these videos, so I don’t know what’s been done to them.

Can anyone help?