The battery on my Asus U6S laptop is just over three years old. Unsurprisingly, it can barely hold a charge anymore, in part because the person who used it most (I'm looking at you, Mrs. Hassle-Free PC) kept it plugged in all the time. As I've mentioned in the past, that's a surefire way to reduce a battery's longevity and capacity.
Needless to say, a replacement is long overdue. Just one problem: Asus wants $90 for a new battery. And that's not at all unusual: I've seen laptop batteries selling for as much as $150. Crazy!
Fortunately, I know where to go to find cheap laptop parts: eBay. And, sure enough, with a little searching I found a U6S-compatible battery for just $37 shipped. The seller has an excellent rating, and the battery comes with a three-year warranty. Score!
Your mileage may vary, of course--there won't always be such killer deals for every laptop make and model. Also, I should note that there's a bit of a safety risk involved in purchasing cheap, third-party batteries. On the other hand, even manufacturers' own batteries have been known to have problems, so you might as well save a few bucks.
Batteries aren't the only laptop part you can find cheap on eBay. As I wrote back in 2009, a worn-out keyboard is often very cheap and easy to replace. I did a five-minute surgery on a Dell laptop, which had sticky keys and rubbed-off letters, and spent a grand total of $12. The result: a laptop that looked and acted like new--keyboard-wise, anyway. Again, your mileage may vary.
Finally, if your laptop screen is cracked, burned out, or otherwise not working, look to eBay for an affordable replacement. Prices and availability definitely vary widely here, and replacing a screen isn't nearly as quick and easy as replacing a battery. The seller may offer instructions, or you may have to do a little online reconnaissance to find help. But even if you hire someone local to do the labor, it'll probably end up costing you a lot less than the manufacturer would charge.
If you've had any experience with these kinds of laptop part replacements, tell me about it in the comments!
Contributing Editor Rick Broida writes about business and consumer technology. Ask for help with your PC hassles at email@example.com, or try the treasure trove of helpful folks in the PC World Community Forums.