Moving files in finder vs. copying

Up until today, I never had this problem. I have all of my files inside of a folder on my desktop. Inside this folder, is another folder. I have been "moving" files within these two folders, but instead of moving, they are "copying"

I really don't want to have these files making copies. There are more than 100 gigs of files I want to move. Is there any way to change the default actions of this folder back to moving rather than copying?

Thanks a ton!

are you moving from one drive to another or on the same drive..

same drive, same folder on that same drive.