Emachine powers on but keyboard,mouse, and monitor quit working

Hello, my son's keyboard, mouse, and monitor quit working, but the power was working on the tower. We tried everything and finally turned to Google. What worked for us was while the power was still on, we unplugged the main power on the inside of the tower. We then unplugged the tower, and plugged the main power back in inside the tower, and then plugged the tower back in. It sounds crazy, but it worked and my son is back in business!