1. No power from the wall socket: Use a live power outlet. In rare cases, the power cable may be defective and may require replacement. Check the power cable on another working PC. Plug in a lamp or any other electric device to see if you have a live outlet.
2. Incorrect voltage setting on the PSU: Select the proper voltage setting (220-240V) on the back of the PSU. WARNING: If you have switched on the PC with the voltage set to 110-120V and with a mains supply of 240V you may have blown your PSU beyond repair at worst or blown a fuse at best. Be careful!
3. The front panel power switch’s connector to the motherboard is not fixed correctly or has come off or is defective: Check the motherboard manual and fix the lead (wires) from the front panel switch to the motherboard correctly. If there is still no power, try a different lead.
4. The front panel power switch is defective: Replace the switch. In case you do not want to get a replacement, one option is to use the reset button. The only problem with this is that to cut the power to the system in case of system hangs etc., you will have to switch off the power from the mains wall outlet rather than from the front panel.
5. The power supply connections to the motherboard are not correct: Check the power connections from the PSU to the motherboard. Refer to the motherboard manual and identify the correct connection points.
6. Not identified; non-PSU related problem: After attempting all the above, if the system still doesn’t power up, it is time to look elsewhere. Disconnect all the drives and see if it is powering up. (Note: Pull out the power cord when removing or disconnecting something.)
If the system is powering up, then start reconnecting the drives one by one to identify which is defective drive. If the system is not powering with all drives disconnected, remove the other adaptors one at a time and checking to see if it is powering up. Leave the video adaptor for the last. If you are able to isolate the problem to one of the adaptor cards, verify that the slot and the adaptor cards are compatible. Then try plugging it into a different slot and see if the system powers up before discarding it and going for a new one. If the system is still not powering up, then you either have a defective PSU or a defective motherboard. If there is a burnt smell, then most probably either one of them has been fried. Look for burn marks on the motherboard. Sometimes the PSU and motherboard may be incompatible. If the motherboard looks fine, replace the PSU, since it’s cheaper! Check the relevant sections of this guide for troubleshooting hints for the other components.