Kevin has an HP laptop with a 500GB hard drive and he's getting warnings that he's running out of space. How can he see what is taking up all that room and what can he get rid of? Leo says he can delete temporary file, because they aren't needed. By implication, that's just a repository to place files temporarily. He'll want to be sure to only delete files when other programs aren't running. He doesn't want to crash out an application that may be using a file in that temp folder.
Leo recommends Disk Cleanup to clean up the hard drive and get rid of unnecessary files. Leo also says that this is an indication of a sloppily written app that doesn't clean after itself. Kevin should reboot the computer, clean out the temp files, and then reboot again.