Sorry if this is the wrong place, but this is driving me insane.

Yesterday I added a second monitor via HDMI to my machine (the original is via VGA). I couldn't get the HDMI one to fill the whole screen, so I was playing with a lot of things (google isn't always good) and will have inadvertently done something stupid (including drivers updates etc). I finally figured out that despite what it said on the box, it doesn't cope with the right resolution, so I reduced it - all good so far.

Then while I was typing somewhere, I hit ctrl+shift+left, and the screen flipped. I figured out to do UP, and all went back to normal. Problem is I use that key combo a lot, and can't switch it off. It doesn't work with CTRL+ALT combination, only CTRL+SHIFT. It also doesn't happen on either of the other two accounts on this PC. I've compared the drivers in use, and they're all using the same version. The hotkeys are completely disabled for the other accounts, it would seem, and only on my account (where I was doing all the messing around).

Any ideas how to switch off the hotkeys? I have no "graphics" option on right click of the desktop, and nothing in the system tray. I also can't roll back drivers, it would seem.

I'm running Windows 10 (Ver 10.0.16299), on an ASUS M5A78L-M USB3 desktop, AMD Bulldozer FX-6300 6 Core 3.5Ghz with the inbuilt ATI Radeon 3000 GPU (driver ver 8.970.100.9001).

I guess worst case is I could delete the account and recreate it, but I'm concerned that a) that won't fix it and b) I'm stupid - I'll do it again.