The most important parts to run the pc are:
The power supply-it is used to power all the things such as all the internal hardware.
It depends on what watts it runs at.
The Motherboard-this is the "mother" of the pc that is used to run everything inside the pc. This is the main chamber for everything inside the pc, if you didnt have this then your pc wont run. the motherboard powers everything in the pc such as the GPU,CPU,RAM,ROM,WINDOWS and the Graphics card