I'm only capturing the image in a window on the top left

[rachalmers]

I'm running on a Toshiba L630 Laptop. I'm trying to capture an old game on it, but no matter what settings I use I only manage to get the display shown in the top left of the available window. It's the full image, but much reduced into the top left quadrant. I've attached a reduced-size screenshot of the whole window, showing the game in the top left corner.
I think I've tried about everything I know to get this full screen. Which I might add, when the game is playing on the laptop, it is fullscreen.
Just that the capture isn't fullscreen.
On the Laptop screen, the game window is centered horizontally, with a small letterbox effect on either side and aligned top and bottom.

 

[koala]

What happens is this: The game runs in exclusive fullscreen mode and switches to a different (smaller) resolution than your Windows desktop resolution while it is active. In OBS, you set the Windows desktop resolution as base resolution, so you see the Windows desktop covering your whole OBS preview, but the smaller game resolution is occupying only the top left corner.
The game appears fullscreen to you, because the monitor adapts and automatically zooms your game.

You either need to play your game with the same resolution than your Windows desktop resolution, or you need to change in OBS Settings->Video your base (canvas) resolution to the resolution you play your game in. You can also set the game source to "fit to screen" (right-click the game source->transform->fit to screen, but this will upscale your game and make it blurry and generally make the quality worse.