I was wondering two things about “Snowy”, one of my PCs:

Why was the fan so noisy?

And why did it occasionally stop dead in its tracks? Typically when the machine was busy, and particularly noticeable while playing games. No warning, no graceful shutdown, just power off.

I had been planning for a re-installation of Windows, and started the process when it shut down again.

So I decided to open it up. Checked a few connections. Nothing obviously loose.

Then I looked at the fan. Caked in dust.

Using a vacuum cleaner, a duster and a pen (the latter for poking in to disturb the dust where nothing else would reach) I cleaned around the motherboard, and particularly on and around the fan.

What appears to have been happening is that due to the dust, the fan was having to work harder than usual. And when the CPU got busy/hot, the fan couldn’t cope, the CPU overheated, and something smart in the PC was cutting the power to stop it causing any damage.

Since the cleaning, the fan is not only quieter, but there haven’t (touch wood) been any more sudden shut downs.