The Online Family answers:

When it comes to warranties, you have a few options.  Most computer sellers offer a 90-day or one-year warranty with your purchase.  This helps if your computer doesn't work 100% correctly right out of the box, or if you need support with setup.

Still, families tend to keep computers for at least three years. So to play it safe, think about going with the manufacturer's extended warranty plan or customer care package. These optional plans cover hardware and provide tech support, usually for a cost of $350 or more.

That said, if you have a laptop, toting it around means an increased chance of damage to the hardware. For laptops, consider extending your warranty to up to four years.

In any case, make sure to read the fine print before you shell out the extra money.  Does the warranty offer on-site support? If you need a new part, do you have to pay the postage to send your computer back to the manufacturer? Is there a toll-free number you can call 24-hours per day, or do you have to use online support to solve your problems? Does it cover accidental damage?