The phone call started with “I heard a loud bang and I could smell something burning so I turned my computer off. Have I lost all my data? What do I need to do?”
It’s all OK. It has happened a few times over the last few years and it doesn’t seem to matter what the make model of the PC is. The common factor seems to be the dust. If you have your PC on the floor and it is sitting on carpet or a very dusty environment the fans suck the air in from outside to cool the electronics. The problem with that is that your feet are usually under the desk moving over the carpet and lifting the fibres into the air. The heatsinks on the components inside your computer that get hot then collect the dust and the air doesn’t flow around them the way it use to.
This means that the fans usually get louder because they try to spin faster to compensate for the higher temperature. The fan seems to go out of balance and start to become noisy. The power supply will also collect the dust and heat up and draw more power until it finally gives out and you them make the call to me about the noise and the burning smell. Replacing the power supply is not a difficult job, and you information should be OK.
I like to use generic ATX form factor cases and power supplies because they are readily available quick and easy to replace. If you have the pretty, thin desktop pc cases, the power supplies are not so easy to source and in most cases, I will change the case to a more common available style to get you back online quickly.