This simple device is not a 'waste of money' as I had thought. Even turning on an appliance in your house while your computer is on can create havoc with your hard drive. Avoid the cheapest protectors - invest in a good one.
Electricity does fluctuate, and some nasty zappy thingies can come over the telephone line as well.
You will lose ALL of your information except for the small bits put on floppy discs - if you bother to do this. Nearly everyone that I know has lost precious information. Believe me, you will feel sick when your system crashes and you do not have a back-up system. The cheapest way to go is with a basic tape drive. Get the gigabyte zip drives if you can afford it.