I recently bought some new parts to repair an old computer that fried. I replaced the Motherboard, the CPU, the Graphics Card and Power Supply. After putting the new parts in and after checking it over multiple times the computer wouldn't start. I looked it over a few more times and couldn't get it. Finally after taking it all apart and putting it back togethor it turned on. The keyboard and mouse didn't do anything so i restarted it. After that the computer wont do anything, wont even come to the bios screen. Any tips?