The HP Computer Will Not Boot Up & the Light in the Back Is Blinking

Before assuming your PSU has gone belly up, check the wall outlet or power strip your computer is plugged into. If the PSU doesn't receive enough power, it can't boot your computer and blinks to alert you to a problem. Move to a different outlet, or plug your cord directly into the wall and bypass the power strip. If the light shows a steady green after this experiment, your previous outlet or power strip was faulty. If it still blinks, check the power cord itself for signs of damage, such as kinks or tears in the insulated cover.

Sometimes your computer's components and PSU can hold onto a residual charge that prevents it from operating properly. Discharge this excess electricity by disconnecting all cables and cords from your desktop tower and holding the Power button down for at least 10 seconds. Plug the power cord back in and check for the light. If it still blinks, remove the cord again and flip the little red switch near the PSU plug connection. This is the voltage switch, which can be toggled between 220V and 115V. Move the switch to the other position, wait five seconds, then flip it back to its original spot. Be sure the switch is back where it started before plugging your power cord in to check for the light.

A desktop PSU is rated for a certain wattage, and can only handle components up to that number. If you have recently installed a more powerful component, such as a graphics card or CPU, you may have exceeded your PSU's wattage rating. Unplug the power connectors from all your internal components, connect the power cord to the back of the tower and check the light. If it's steady, one of your internal components caused the issue. Plug each component back in, one at a time, and check the light. When it starts blinking, you've found your culprit. Remove the component or upgrade your PSU to a higher wattage.

If everything else seems operational, from the wall outlet to your internal components, your PSU may have failed and require replacement. Check your PSU's label, as well as the labels of any newly installed components, for the exact specifications and power requirements to ensure you find a new unit that is powerful enough for your setup. If replacing the PSU doesn't affect the blinking light, your motherboard may have failed. Seek the help of a professional computer repair technician or contact HP if your machine is still under warranty.