Why is my HDD space available is incorrect.

When I open 'About this Mac' I can see in the breakdown of my storage that apparently I have nearly 40GB of movies stored on my Mac. I keep my movies well organised within the Movies folder of my Home directory. When I look at my home directory and get info on it, I see that the size of the entire home folder including all my music and documents is less than what About this mac is telling me the Movies folder is.

It seems like there are some files that I can't get access to but are using space on my HDD. If anyone has any idea of how to fix this it would be great.

Thanks in advance.