So I got the same problem with HD4000. I have Sony HMZ-T1 hmd and a lcd monitor
connected to the passthrough in the control box of the HMZ-T1, which makes the lcd active
when I switch off HMZ-T1 display. Suddenly one day the lcd remained blank when I switched
off the HMZ-T1 to use the monitor instead. I found this thread and tried what they discuss
in the beginning about deleting registry keys. That didn't do it so I tried killing some processes
in task manager and found that when I kill igfxpers.exe I get image on the monitor, but something is
still wrong. I can't set resolution on monitor to 1920x1200.
So I was happy to find the devcon trick at the end of this thread, but I discovered it doesn't work
in Windows XP. Because XP want to reboot after devcon disable device.
Well, I can soon do devcon (I hope) when I get Windows 8, but we'll see if it works on my setup.
But it seems the error is in igfxpers.exe, don't know if that's been established earlier.
I really hope Intel can resolve this soon!!