Fullscreen not working properly for games while connected to monitor

Hello all. I'm having a problem with toggling fullscreen while playing games. I've been Googling and trying to find an answer for some time, but no dice, so I'm hoping someone here can help. I should note that I'm playing old games here, nothing more recent than the 90s.

Let me describe the problem. It's manifesting in different ways, so I'll give three examples.

1) When I use Kega Fusion (Sega Genesis emulator) in windowed mode and I toggle fullscreen, the screen temporarily goes dark and then comes up again with the program minimized to the taskbar. When I left-click on the program in the taskbar, the screen temporarily goes dark and then goes back to my desktop with the program minimized to the taskbar.
2) When I use Dosbox in windowed mode and toggle fullscreen, the screen temporarily goes dark and then comes back with Dosbox in the windowed mode it opened in.
3) When I play Full Throttle, it opens in fullscreen, no problem. However, if I push the Windows button to go back to my desktop, the program stays minimized in the taskbar and I can't get it to open in fullscreen again.

Some things to note:
- This only happens when I'm connected to an external monitor. I've tried switching between VGA and DVI connectors (my laptop does not have HDMI) but the problem doesn't change.
- I've checked to make sure that the fullscreen resolution matches my monitor resolution, but no change.
- I've changed the resolution and tried a few different resolutions, but no change.
- This hasn't always been a problem. It started happening a few months ago and I haven't been able to solve it. I've tried updating and rolling back the drivers for my monitor, but it hasn't made a difference.

Hope I'm able to find a solution. Thanks!

A helpful Redditor assisted me in solving the problem! Fullscreen not working properly for games while connected to monitor : windows7

I'll post this here in case anyone else has the problem. The Redditor suggested:

"The only other solution I can think of, aside from reinstalling Windows, involves changing some registry values:HKEY_CURRENT_USER->Control Panel->Desktop: ForegroundLockTimeout=200000(decimal)"

And this fixed the problem!