Windows 7 moves/resizes windows on monitor power cycle

Also want to thank you because I was having this same problem, everywhere else on the internet was saying it could be a hardware incompatibility between my monitor and my (new) video card, which would be awful. The sticking point seems to be that there's this "simulated" entry needed alongside the entries for the actual devices (I know it's needed because I tried to delete it, and Windows recreated it on restart) and for some reason Windows made certain settings different. Changing the keys you pointed out so that the keys in the "simulated" entry match the real one fixed the resize issue.

Something else it does when the monitor turns on is that it moves my windows to the side, even though it no longer resizes. I'm guessing that's another entry mismatch and will play with it on my own.

Thanks again!

I built up an new computer, and got the same problem..

After changing registry as noted above, it gets a bit better, but it doens't do the same if I turn off the display manually, or if I let the computer go to sleep.

But I have 4K display, with some higher resolution, using displayport cable (only cable that can be used for this resolution), and this is very annoying..

My setup is:

Windows 8.1 x64, Sapphire Radeon R9 280x, Samsung 28D590

Replying to this because there's an interesting pattern here, between what you're pointing out and some other posts. I started getting this problem (and fixed it with the great registry change advice above) after installing my new video card, which is also in the Radeon R9 200 series (a 285 in this case). So it could be an issue with this kind of card.

I'm just going to add some more detail in case it helps anyone else who finds this topic:

I have set the real and "simulated" keys to have all the same values. However, the windows will still randomly "slide" to the left a bit when I turn my monitor on.

Not sure if this happens to anyone else, but, when I turn my monitor on it makes the disconnect and reconnect chimes, as if the monitor is a USB device being unplugged and then plugged back in. I don't know why it does that now, but I can't help but think that they're related.

Yes the same things happens to me (as reported years ago). It's definitely related to the unplugging sound: an earlier version of my system's driver did not cause the sound and did not resize or move windows.

I just experimented a bit more and finally made a little progress: I hooked up an identical 1920x1200 monitor to an identical machine, with the original registry, and get the same misbehavior, as expected. Hooked up an older 1280x1024 monitor instead: Windows makes the plug-in/out sound when you plug in/out the DVI plug (with the monitor turned off), and windows get bluntly rearranged, seemingly to fit the 1024x768 simulated screen size (I didn't measure exactly). But powering on or off this particular monitor does not cause the USB sound and does not rearrange windows.

So some monitors advertise a power-down as a plug-out, and some don't. Or at least, that's the way the graphics driver or Windows itself interprets some signal received through the DVI cable. The unplugging sound and window rearranging also occurs if Windows orders the screen to go to sleep, by way of the Power Options, and it seems odd to me the monitor should respond to that command by signaling anything. But I really don't know.

Also, I checked with sysinternals process monitor what happens when powering down the monitor. Alas, the very first thing reported is csrss.exe accessing the SIMULATED_8086 registry key. I think that's too late: Windows already thinks the monitor was just unplugged. And whatever it is that convinces Windows the monitor was unplugged, happens deep down in device drivers, outside of the scope of process monitor, and of me.