A: I've seen this problem before, with sleep being disabled on a Windows 8 machine. To fix it, first run the powercfg /a command

 <code><strong>powercfg /availablesleepstates</strong></code>

to check that it is indeed the graphics disabling the sleep state (S3), as confirmed in the output below:

C:\Users\john>powercfg /availablesleepstates<br>
The following sleep states are available on this system:<br>
Hibernate<br>
Fast Startup<br><br>
The following sleep states are not available on this system:<br>
Standby (S1)<br>
The system firmware does not support this standby state.<br>
An internal system component has disabled this standby state.<br>
Graphics<br><br>
Standby (S2)<br>
The system firmware does not support this standby state.<br>
An internal system component has disabled this standby state.<br>
Graphics<br><br>
Standby (S3)<br>
An internal system component has disabled this standby state.<br>
Graphics<br><br>
Standby (Connected)<br>
The system firmware does not support this standby state.<br><br>
Hybrid Sleep<br>
Standby (S3) is not available.

It's important to make sure you have a driver installed for your graphics device, so the OS knows how to suspend and resume the hardware. The times I've seen this problem occur are when a system has multiple GPUs and one is not used and so has no driver available--this situation will disable sleep.

Also make sure you use the manufacturer's driver, to ensure sleep availability. Additionally, if the computer starts using one graphics device, such as the onboard, but then that device is disabled within Windows because, for example, a separate GPU card is used, then sleep is disabled.

Instead of disabling the onboard, configure the display so it will not be used, as the screen shot below shows. These basic steps should resolve the problem.

displaynotusedsml
Configuring the Display