It is almost always dust
Laptops and desktops pull air through a heatsink, and over a few years that heatsink packs with dust and hair until air stops moving through it at all. The fan then runs at full speed permanently, because the machine is trying to cool itself and failing.
This is why the symptom appears gradually. Nothing broke — the cooling just stopped working, one month at a time. Homes with pets reach that point noticeably faster.
Thermal paste dries out too
Between the processor and the heatsink there is a thin layer of paste doing the actual heat transfer. It hardens with age, and once it does, heat stops moving even through a clean heatsink.
On machines past about four years old, cleaning without replacing the paste fixes half the problem. We do both, because doing one and not the other means you are back in six months.
What overheating actually costs you
Modern processors protect themselves by slowing down — so an overheating machine feels slow long before it shuts down. People replace perfectly good computers over this.
Sustained heat also shortens the life of everything near it, batteries especially. A laptop that runs hot for a year is a laptop with a battery that aged like three.
Things worth trying first, free
Take it off soft surfaces. Beds and couches block the intake completely, and a laptop on a duvet is running with no airflow at all.
Check what is using the processor. Task Manager will tell you in ten seconds whether something is genuinely working the machine or whether the cooling has failed.
If it is a desktop, look at the intake filters. Sometimes that is the whole job.
How often this needs doing
Most machines want a clean every two to three years. Sooner in homes with pets or carpet, later in an office. A desktop that sits on the floor collects far more than one on a desk.
The tell is not the temperature, which you cannot feel, but the fan. If it runs loud during things that used to be quiet — browsing, email, video calls — the cooling is already struggling.
It is genuinely preventative work. A clean costs an hour of diagnostic time; a processor or board that cooked costs considerably more, and often is not worth repairing at all.
Answered plainly.
How much is a clean and repaste?
Diagnostic is $50/hr and the work is usually straightforward. We quote before starting, and if the machine is not worth doing we will say so.
Will compressed air do it myself?
Sometimes, on a desktop. On a laptop it usually just moves the dust deeper into the heatsink, because the packed layer is behind the fan rather than in front of it.
My computer shuts down when I play games. Same thing?
Almost certainly. Load generates heat, and a machine that cannot shed it protects itself by cutting power. It is a cooling problem, not a graphics problem.
Can overheating damage my files?
Not directly, but sudden shutdowns can corrupt what was being written at the time. Worth having a backup before it becomes a habit.
Not quite your problem? Start the troubleshooter and it will narrow it down, or see what everything costs.
Tell us what it’s doing.
Quotes are free, and we point you at the cheapest thing that actually solves it.