I’ve had a few computers of my own break after a few years of use, and I’ve seen computers owned by friends and family do the same thing.  They either slow down (even running the original software they shipped with) or crash more often (kernel panic/BSOD, freezing, etc).  All computers eventually fail, and not always in easily explainable ways.

For example, my first computer was a MacBook Pro.  After about 3 and a half years of use, it started to freeze a few times a week, then reliably every day.  OS X would stop responding; my mouse moved, but absolutely nothing responded.  It ended up lasting more than four years, but I was in the habit of saving my work every time I paused in typing, and kept rigorous backups.

I’ve also seen old family computers running early versions of Windows completely freeze (no mouse movement) just after completing startup.  And I’ve seen a 4 year old 12″ PowerBook G4 run like molasses even after having been wiped and reset to factory settings and OS.

What causes this?  Do the electronic components break down over time?

Solution:

The environment has an effect on your computer.

Temperature changes make electronic components expand and contract, if they do that a lot of times eventually connections will get damaged and even break. This results in different resistance which reroutes the power and causes components to behave in an unexpected different way.

This is why in some data centers whole server rooms are cooled with gas to keep the temperature at a constant level, besides keeping the servers from overheating this also keeps the hardware lifetime.

Humidity changes are also not very good for electronics, this can lead into different conductivity; or in the case of condensation, it could even short circuit an electronic circuit.

This is also why they very tightly seal electronic circuits on a ship, even though the rain and sea can’t reach the electronic circuits. That way, the circuits don’t suddenly start to malfunction when they are in the middle of the sea. Better to be safe, than to be sorry…

There are other factors like (direct) mechanical or magnetic damage, as the environment is not the only cause of damage. An example is a hard drive running out of its lifetime or the computer being placed near magnetic materials. But components like hard disks are known to not keep on for more than a few years; while not mentioned explicitly when sold, one should keep track of its state as a good habit.