Improving motherboard with a graphics card and a more powerful power supply

[Powdy22]

Hello, I would like to ask you about one snag.

I decided to upgrade my HP personal computer with the original parts from the manufacturer with new ones, which will allow me to play some game. The graphics card that I want to install on my PC requires a minimum power supply of 300W. The current power supply, which is in the PC from the factory, has a power of 180W and the board and power supply have only 4 pin CPU and 4 pin ATX main power (not 20 or 24 pin but only 4 pin ATX main power), for example as HP Pavilion 595/590. Of course, the board has a slot for a dedicated graphics card, so it can definitely be fitted.

I wonder if I buy a new power supply that offers 300W of power and usually has a 20 + 4 pin ATX main power connector and I am forced to use only 4 pins from it, will it be able to supply all the necessary power for graphics card and make it work with the whole PC?

Thank you very much for your answers and advice.

[itsmyname]

> will it be able to supply all the necessary power for graphics card and make it work with the whole PC?

Are you purchasing a graphics card that has its own socket (4-pin? 6-pin?) to supply power to it? 

Presumably, your selected power-supply will have an additional lead for powering the graphic card ???

Take a close look at the 4-pin socket on the motherboard, especially at the layout -- some pin-holes will be square, and some with have two beveled corners.  Can you find a matching arrangement somewhere on the 20-pin connector? Not all of the 20 pins will need to connect to the 4-pin socket on the motherboard, if there is "clearance" around the 4-pin socket to let the other 16 pins to NOT fit into anything.