This is the EASY way to remove ATX connector pins without any extra tools, all you need is a regular plastic ballpen mine:
1) Push the open end of the mine over the pin:
2) Pull on the cable to remove the pin:
ALL DONE! The ballpen mine pushes down the two flaps that hold the pin in place:
Don't forget to lift the flaps a bit with a knife before putting the pin back into the plug: