None of the above happened to me today, because Speccy had headed it all off at the pass. The software had informed me that my PC was getting a bit hot, before any problems had begun to manifest.
However, I might have over-stated how quickly I grabbed my dust-busting tools. In reality, I did the laundry and a bit of washing up, then generally tidied up. None of this was important to the job in hand, but for one major fact - I was killing time.
You cannot dust inside your computer while it's still warm. Wait half an hour after switching it off, before you open up the back.
There are two reasons. The first is that the PSU will be hot and you might hurt yourself. The second is that you're exposing the inside to the open atmosphere without the protection of the casing. There's moisture in the air. There's electronics inside.
This will naturally be the longest half an hour of your life, but when it's finally over find something metal and touch it. Not the PC! This is solely to earth yourself, just in case you're carrying static electricity.
Now, if you haven't already, take out all of the cables from the back of your computer tower. The power cable should be self-explanatory. You shouldn't be inside your PC while it's still plugged into the wall. That way leads to electric shocks and hospitals.
The rest (head-phones, microphone, webcam, memory sticks, keyboard, mouse etc) is simply because you're not staying at your desk. You and your computer tower are heading outside!