Why does a PC or laptop in sleep mode suddenly wake up? There can be many reasons, and all are simple to fix, as our Helproom Editor explains. Here's how to stop your PC waking up from sleep mode when you want it to snooze on.

QUESTION My Windows 7 PC has developed a problem with sleep mode, often waking for no apparent reason. I don't think it's the mouse or router disturbing the PC, since the problem began only recently. Can you help? Scrivers

HELPROOM ANSWER There are many reasons why your PC might wake from sleep mode. The mouse is the most common culprit, since it's able to detect small movements, but it's not the only stone under which you should look.

Windows keeps track of the events that cause it to wake from sleep mode; you can access this information using the powercfg command from the command prompt (type cmd in the Start menu Search box and press Enter to display a command prompt).

The specific command you will need is powercfg -lastwake, which will return information on the device that woke your machine. You can then locate the culprit in Device Manager and turn off its ability to wake up the PC. Choose Properties, Power Management and deselect ‘Allow this device to wake up the computer'.

You can often enable or disable wake-up events within your PC's Bios, too. Have a look there and make sure that all unnecessary wake-up events are disabled. Look for an onscreen message when your PC is booting to learn how to access the Bios; you usually need to press Del or F1.

Sleep Mode

Find out why your PC keeps waking itself up

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