Who are you hiding things from?
If it's your spouse then simple delete should be adequate unless he/she is very computer savvy.
If it's the authorities, you're wasting your money. There are ways of recovering information from computers that you think are "clean" including the efforts of these eliminator programs.
The best thing, of course, is not to download or have anything on your computer that shouldn't be there.
Note ignore "testimonials" - they are most likely written by the same people who wrote the program.