I built a personal computer from scratch and installed a windows operating system. I also helped my friend troubleshoot the issues he had on his computer when he was assembling it. There was no display when he tried to turn it on but they were two issues he had with it which made it an easy fix. He hadn't connected the front io connectors correctly which was his first issue. But it still wouldn't display but the reason was the Graphics Processing Unit (GPU) wasn't seated properly.