I was wondering how to clean a computer motherboard knowing that using conventional cleaning products is obviously prohibited.
What is the most effective and least dangerous way to remove dust?
Use compressed air from a can. Do not use air from an industrial or an electric pump (yes, people have done this.) Make sure that the can is upright when you spray, or it might come out too cold.
An even better solution is to use pressurized electronic contact cleaner. Make sure you use electronics contact cleaner, which is almost pure alcohol. Do not use any other kind of alcohol, because the water content will be too high, and you'll ruin your electronics.
Using a can of compressed air spray the surface of the motherboard from 6 inches away.