No, a 20+4 pin cannot be connected to an 18-pin motherboard.
No, a 20+4 pin cannot be connected to an 18-pin motherboard.
This setup isn't a standard HP system. It's likely a different brand or model with its own unique connector design. You may need a compatible adapter, but verify it works with your specific motherboard model.
That is an HP specific connector used primarily on their workstations computers as far as I know. You will need to get an adapter. The pin-out is not the same so you cannot plug it in without damaging your components. And btw. please clean out that cpu cooler and if you have some, replace the thermal paste, it's probably dried up by now.
It has been cleaned recently, and the thermal paste is back in stock. The flashlight light gives it a dusty and unpleasant appearance.