Sorry Andy,
For me, a "dark monitor", is a monitor working, but displaying all pixels with black. My bad.
I still don't think your description match my point, as the HDMI monitor isn't detected in windows.
Additionally, the VGA monitor is 1280*1024, and the HDMI is 1920*1080. The image sent by the graphic card to the VGA is in the 1280*1024 res. If the HDMI signal were sent to the VGA cable, why isn't it in 1920*1080 ?
Regards,