We have earlier seen how you can prevent Windows computer from going to sleep. In this article we will tell you how you can prevent your computer from waking up from Sleep unexpectedly.
It happens to most of us, we set our PC on Sleep mode and it sometimes suddenly wakes up for no apparent reason; even when we may not have touched it. And its really annoying, leaving you wondering what may have made your PC wakes up automatically.
This may occur due to a hardware device having been recently attached to your PC or because of any program which may have been scheduled. If you experience this annoyance frequently, you must check the following things:
A hardware device might be keeping your computer awake. USB flash drives and USB mice are common devices that can keep your computer awake. You must keep the drivers of all your attached devices updated to their latest versions.
To prevent a device from waking your computer
1. Click on Start and go to Control Panel and open Device Manager.
2. In the list of hardware categories, find the device that you want to prevent from waking your computer, and then double-click the device name.
4. Click OK.
A program or scheduled task might be waking your computer. By default, Power Option settings do not allow scheduled tasks to wake the computer from sleep or hibernate. However, some programs might awaken the computer if these settings have been changed.
To prevent programs from waking your computer
1. Click to open Power Options.
2. On the Select a power plan page, click Change plan settings for the plan that you want to change.
3. On the Change settings for the plan page, click Change advanced power settings.
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UPDATE: Mike Vanderkley adds in the comments:
You can use powercfg /lastwake to find out what last woke your computer.