Want to really delete a file? Instead of choosing Empty Trash from the Finder menu, choose Secure Empty Trash. The difference is that the latter will overwrite the bits for that file, completely erasing it. The former only forgets that the bits were a file in the first place, but leaves them there until they are overwritten by something else. It is possible in that case to sometimes retrieve the file using special software. You can also go into Finder, Preferences, Advanced and make this option the only one.
Mac Video Tutorials and Tips for Apple Users
