I think the HTPC section was the right place for this question. HPD is very simple. If it is not asserted, the source is supposed to go to the no sink connected state. When it is asserted, the source is supposed to get the EDID of the sink and authenticate. If it is de-asserted and re-asserted, the sink is supposed to start the whole process over. Be aware that some source side chips are capable of detecting a connected sink without HPD being asserted. I suspect the problems you are experiencing are not caused by Microsoft's operating system, but by the drivers supplied by the hardware maufacturer.