The following udate provided by the windows update system:
nVidia - Graphics Adapter WDDM1.1, Graphics Adapter WDDM1.2, Other hardware - NVIDIA GeForce 8500 GT
Download size: 226.0 MB
You may need to restart your computer for this update to take effect.
Update type: Important
nVidia Graphics Adapter WDDM1.1, Graphics Adapter WDDM1.2, Other hardware software update released in October, 2012
Causes the PC to lock up and the only way to recover is to return to a previously restored version of the system.
I have tried a later version from the nVidia website and this has the same effect.
I have current inhibited the automatic upgrade option to prevent the system locking up.