Many motherboards fail due to dielectric capacitor dried up, losing capacity to store energy. Dielectric capcitors genrally last about 10 years, then it will dry up. You can restore it by curing. which is a simple step of leaving the computer on, and moisture will be absorbed back into the malfunctioning capacitors due to warmth in a few days.

Generally again, computers last longer if left with power on constantly, to keep things going steadily and avoiding stress from thermal expansion and contraction, which cause earlier failure of many components. computers left on for ten years at a stretch functions very well. Hdd might have moving parts such as bearing worn, but those with claims of 230,000 hours(mean time) between failure will survive.

Then you have lithium battery which are recharged constantly and can last 10 years anyway. If it is depleted, however, you will find that you no longer can boot properly. Using mini post card in PCI slot, I have found that there is a way to revive the lithium battery. You might turn power on/off for ten times to let the inductace kick to charge the lithium battery a little, then the steady charge of DC power supply will revive the battery and complete the boot of your operating system. Then don't turn off your computer, keep it running until the lithium battery is fully recharged. this may take a day or two. You can always replace the lithium battery. But I bought a batch cheap on ebay, and they are already ten years old. They did not last long on my older motherboards.

These easy fixes may come in handy, if you buy older motherboards, and fool around often. You might now ask how to fix up hdd after a few years of usage?

Well, some heads have pigtails and they can not be fixed. You get more and more corrupted sectors as it wears. Newer hdd with surface coatings will last forever if the bearings are exectly placed horizontally. Any offset from horixontal will have uneven wear on air bearings. Then there are the really old 4gb or less hdd that can last forever. I love to use those with WinME. But then I love tiny Linux livecd even more, they don't use hdd at all.