Windows 7 Sleep requires graphics driver?

Solution 1:

The driver you were using previously was likely reporting the device power capabilities for the device incorrectly. Device power states D0 and D3 are assumed to be supported by all devices, but for PnP devices, the driver must indicate if the device supports D1 and D2.

http://msdn.microsoft.com/en-us/library/windows/hardware/ff561058(v=vs.85).aspx http://msdn.microsoft.com/en-us/library/windows/hardware/ff559825(v=vs.85).aspx http://msdn.microsoft.com/en-us/library/windows/hardware/ff543162(v=vs.85).aspx

Solution 2:

Without a driver for the video card, how would the system know how to put it to sleep or, more importantly, return it to a sane state after waking it up?

Solution 3:

Apparently the old graphics driver was blocking the entering into the sleep state.

Whatever happens exactly when entering into sleep is actually determined by the manufacturer of your computer, so sleep problems may vary between different computer models. It may be that the default driver was handling badly your graphics card and was incapable of turning it off, and by reporting this to Windows was preventing sleep.

For analyzing sleep problems, one can use the powercfg utility.
If you are still curious about the problem, you can revert to the old graphics driver and run powercfg -energy to maybe find out some more information about this problem (then reinstall the new driver).

Many articles exist for sleep problems. See for example :
Evaluate the efficiency of Windows 7 Power Plan settings.