Have you ever had a PC that started making strange whining noises? Even if you've investigated the cause of the noises, which can often sound pretty serious when you hear them, you may not realise the reason for them. The chances are they're caused by a cooling fan with dust in its bearing.

Fans are one of the few components in a PC which have unsealed moving parts. By their nature, they have to be open to the air to suck heat out of the machine and push cool air in. As a result, they're extremely susceptible to all the airborne particles that make up household dust.