Windows 10 stuck in extended screen

Hello.

I upgraded from W7 to W10 almost a year ago today, and although my GPU manufacturer (AMD/ATI) never released a W10 driver update for the card I own (Radeon Mobility HD 4500), I installed the last driver they released for W8.1 and everything was working fine since day one.

The other day, after I unsuccessfully tried to hook up my notebook (HP Pavillion DV4) to a friend's TV via HDMI, my display got messed up. My screen is now extended by default (when I move my mouse left, it doesn't stop at the edge of the screen I see-- my actual screen).

http://imgur.com/a/C6vRb

If I select "Show only on 2" and Apply, my notebook's screen gets dimmed to, like, 95%. I can only barely see it if I point my phone's flashlight to it. And after rebooting, it goes back to extended.

I have tried to disable the ghost desktop in Catalyst Control Center to the same effect-- dimmed screen/back to extended after reboot.

I also tried uninstalling my GPU driver using DDU. When I'm only using Microsoft's Basic Display Adapter, my screen goes back to normal, but after reinstalling AMD's driver, it all goes south again.

I figured it could be something wrong with my registry keeping old/wrong data, but after deleting the entries on "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY" and rebooting, nothing happened.

I don't know what else to do besides formatting, which is the last thing I want to consider. I've tried all the Win+P options, uninstalling/reinstalling the drivers in safe mode, pretty much everything.

Can anyone possibly shed some light on what this could be?

Thanks in advance.
 
You started from the assumption that this is a Windows issue rather than something connected with the hardware. You also say that after deleting registry entries and rebooting that "nothing happened." Deleting things from the registry is risky so does "nothing happened" mean that the laptop will no longer boot up?
 
I'm sorry for the bad wording. I meant nothing has changed. Same old.

My monitor is #2 as you can see in the printscreens. There's no way to change the numbers afaik.
 
Another idea: as admin, go into Device Manager and "remove" both monitors; then reboot and OS should only find the one monitor (laptop) which remains..
 
Having to shine a bright line on the screen in order to see what is displayed is a sign of a failure of the backlight or its inverter.
 
Back