Dell tried this with the LatitudeON feature which shipped in several variations on Latitude laptops. In their version, turning the ARM OS on automatically hibernated the Windows OS. In any case, for some reason, it has not caught on (Dell has also had trouble meeting shipping dates, as they are using a custom Linux distro from DeviceVM, rather than using Android). I almost bought a new Dell just for that feature, and in polling other business users whose machines had the feature in one form or another, I have yet to find someone actually using it. Poor marketing and perhaps targeted at the wrong market. One challenge is whether to power up the hard drive. If you leave it unpowered and just have the ARM and some RAM, you lose the ability to access data on the hard drive, but powering up the hard drive increases the power load materially.