Nothing happens after PC's power button is turned on

Work through this checklist to narrow the list of potential power problems. Take notes as you diagnose the problem; notes will be helpful if you wind up needing technical assistance from a pro. First, examine the board for signs of overheating. You may see scorch marks that are the hallmark of a power surge or blown power components. Make sure the PSU (power supply unit) is providing power to the board. Most motherboards have LEDs that show the board is receiving power. Also, verify the CPU fan is working. If it isn’t, the PC may not start properly. If you’re still having problems, remove your system’s expansion cards, such as the modem card and sound card, especially if you just installed a new card. Leave the video card in place. On some motherboards, the components for sound and modem functions may be integrated and thus irremovable. If your computer starts up without the expansion cards, replace the cards one by one until you determine which card is causing the problem. Finally, if nothing else works, swap the processor and the memory sticks with components you know work in another machine and see if the components you swapped work, if you have spare compatible parts on hand. If they do, you know the problem resides in the processor or in the system’s memory.