For example, if the /install /add-driver options were specified, one or more devices were successfully installed and a system reboot is required to finalize installation. ERROR_SUCCESS_REBOOT_REQUIRED (3010): The requested operation completed successfully and a system reboot is required.ERROR_NO_MORE_ITEMS (259): No devices match the supplied driver or the target device is already using a better or newer driver than the driver specified for installation.ERROR_SUCCESS (0): The requested operation completed successfully.For info on other possible values, see Error Codes. Another Sleep cycle brought me back down to normal usage rates, but it would seem something with the Yosemite update (likely some update to the system EFI/BIOS ) likely mucked up something with the graphics in Windows boot-camp.This page lists some of the values that the PnPUtil tool returns. However, I was at normal CPU usage before installing the driver (thanks to 'Sleep' trick mentioned before), and then back at high CPU usage after the driver was installed (didn't make me reboot the system).

I also had an 'Intel Corporation - Graphics Adapter WDDM1.1, Graphics Adapter WDDM1.2, Graphics Adapter WDDM1.3 - Intel(R) Iris(TM) Graphics 5100' Windows Update driver update install today, hoping this would fix the issue, but alas it didn't. It would seem the issue does stem from something with the graphics sub-system, as this forum thread also describes (fixing the issue temporarily by 'disabling transparency'): (Scroll down to entries by: ShotSkydiver Starbucks Co.) 20886d/system-interrupts-making-w10-x86-unusable?forum=WinPreview2014Setup The site where I found this suggestion is here (had to dig through History on Mobile Safari on my iPhone to find it! ^_^):

Intel graphics driver update error 259