This is not a "secret button combo"

Pressing and holding the power button on computers, when there is no power connected, discharges/grounds a lot of the capacitors and other things. Doing this causes things that were "on" and supposed to be "off' to actually turn off, and truly resets everything.

I had an old computer that you could unplug, and it would run for about half a second if you hit the power button again, it wasn't until you did that that it would actually finish being "reset".