If you are like most people when you buy a computer you know to get a surge protector for your computer or have one already.  However what do all the numbers mean, and what other power issues affect your computer?  Well lets start with the numbers.  Joules, lower is better, however cheap surge protectors with low joule ratings will trip incessantly under too much load rendering worthless.  If you can’t keep the power to it on the surge protector is mostly useless.   The next number it usually hard to find but its very important, clamping response time.  Clamping time is how long it take to for the protector to cut the circuit when a surge occurs.  As you can image this is pretty important and the lower the number the better.  Make sure your protector also warranties the equipment you are connecting to it.  Last like all thing surge protectors do wear out, you cannot just keep recycling them because they still supply power.  After about five years the resistors that drive the protectors internals go bad, rendering protectors glorified extension cords.   
                One more note on power problems.  Often you will notice problems with power in houses with bad, or old wiring.  You turn on an appliance and the light flicker or dim for a moment.  Imagine all the millions of electrons shooting around in your computer when something like this happens, and understand that this is a huge problem.  A battery backup or a voltage regulator will not only solve these problems, but make your computer run more smoothly as well.  I highly recommend every computer be put on one or all of these units.