Hiding in your computer are backup files from imaging software, media creation software, and other programs. In most cases they only take up a few kilobytes of space, but occasionally can run up to a meg or two. It's usually safe to delete these files.
A few of the common file extensions are: .bac, .bak, .bck, .bk!, .bk$.
One way to track them down is to do a Search for the extensions listed above. Make sure you put the dot . in front of the file extension. Check the date on the file—more recent ones (like in the last week) you should hold onto while older ones should be OK to dump. To make it easy, sort the search results according to date by clicking the "Date Modified" column header.
Highlight and delete the ones you want to dump.
