Memory storage shows music, movies and photos taking up a lot of space, even after I deleted all the files.

Can anyone help explain this? My storage usage shows that i have over 40 gbs of movies and photos used, but i have deleted all of these files. Can anyone help explain what happened and how to free up this space? This happened prior to my Yosemite upgrade as well. I have a Mac book pro from mid 2009. Thanks!