When your computer first turns on, you're greeted with a manufacturer logo before you see the Microsoft Windows screen; this is called POST (Power On Self-Test) where the computer goes through some checks and sets up the hardware. If any of these tests fail, your computer will stop with a series of error beeps or give an error message like; CMOS CHECKSUM ERROR or PRI MASTER HDD NOT DETECTED.
If you ever find yourself in this situation try the following:
- Remove the power cable and battery (if applicable), then disconnect all other cables and devices attached to the computer
- Hold the power button on your computer for around 5-10 seconds
- Only reconnect the power cable and battery if a laptop, then turn the unit back on
If the computer now works, it can indicate a malfunction in one of the devices that was connected to it. Reconnect them one by one to discover which is causing the problem.
If this isn't the cause, follow the steps below:
If there is no power:
No lights come on and you cannot hear any noises, such as fans spinning.
- Check the power adapter is firmly plugged in at both ends and is turned on at the socket. For desktops, check that the computer and monitor is securely plugged in as well.
- Try a different power socket; one that you know is working with another electrical device
- Try changing the fuse
If there is power but no display:
The power lights come on or you can hear noises from your laptop.
For laptops and netbooks:
- Check the screen brightness hasn't been set too low. To increase brightness you need to press the FN key and the corresponding F key at the top of the keyboard. You user manual should explain how to do this.
- Your laptop may have switched to external display mode. This means it thinks it has an external monitor attached and isn't showing anything on the built-in screen. Press the external display key a few times to see if the display returns. On most laptops, you can do this by pressing the FN key and corresponding F key at the top of the keyboard. Your user manual should explain how to do this.
For desktop computers:
- If the power lights on your computer light up but your screen remains blank you should check the monitor cable hasn't come lose at the back. Unplug the cable and reconnect it.
- Turn your monitor off and then back on; if you see diagnostic messages saying 'no signal' then the cable may be faulty
If your desktop or notebook still fails to start you can call our team on 0844 561 1234. We also have a range of Knowhow™ services, which include: