Sounds like maybe it's trying to display a size that your display is incapable of, & if that's the case, you either need to change your display resolution to something that will work, & then reset the display in the game, or find where it saved the info on the desired screen size, & delete that or change it back.
If the info's stored in a file, you might be able to tell by that file's date -- it would be the same as the time you changed the screen. It might be stored in the game's folder, or in one of the user folders -- look for the name of the game or the company that developed it. If you find the file, maybe you can edit it in Notepad -- if not, maybe you could rename it to see if the game creates a new one.
You can also search the registry using Regedit, looking for the name of the game or the name of the developers, and see if there's a related entry you can find. You might also be able to reset the game by deleting any keys under those names that you find. Always back up first before editing the registry.
There's unfortunately also the possibility that 10 made compatibility settings on its own. AFAIK in that case all you can do is after backing up, deleting references to the game &/or developers throughout the registry, not just keys with the same names, but any entries with those names under other keys too.
