After you install software on your Macintosh, always store the original CD or DVD that contains the program in a safe place. That way, if your hard disk crashes or your Macintosh fails, you can always reinstall the program.
When you download programs from the Internet, keep a copy of those programs (the .dmg disc image files) in a safe place, such as a special folder on your hard disk as well as on a CD or DVD (in case your hard drive fails).
You may never have to reinstall a program after you've installed it, but when you get a new Macintosh or accidentally uninstall a program, a spare copy of your programs and registration keys can make sure you can reinstall your programs and get up and running as quickly as possible.