It ' s a boot issue if your computer is powering on fans are spinning , etc but you still see a black screen . It ' s unlikely to be a PSU issue . Take your computer to a table , remove the case , and try to boot it . There should be a red light on the motherboard . Does the computer power on when it ' s out of the case , and on something like cardboard ? If the computer powers on no red mobo light , but has a red light in the case , it ' s simply touching the case somewhere and you just need to find out where to fix it . CPU light 1 Is the CPU installed correctly ? Are there any bent pins on the CPU ? Is the arrow on the CPU matching the arrow on the motherboard ? . 2 Is the CPU fan connected to CPUFan 1 ? Some motherboards won ' t boot if it doesn ' t have a fan detected for the CPU 3 Is the CPU powered ? There ' s a 8 pin power connector near the CPU that also needs power . DRAM light 1 Is the ram installed correctly ? Check the manual to see how they should be connected . 2 Does the computer boot with just 1 stick of ram ? 3 Is the ram actually installed all the way gotta push down harder than expected with new ram . VGA light Is the graphics card in the slot all the way ? Does the Graphics card have the secondary power it needs from a secondary connector ? If the computer starts up , and there are no red mobo lights . Then the issue is most likely your hard drive .