Goosebumps: Attack of the Mutant doesn't work properly if another window is open. Does anyone have an idea of how I can capture my runs? Usually I'd just use OBS.

I suggest: 1.) Ask in the game's forum to reach players who have experience with the game. 2.) Old PC-games should in general work better on: a.) old original hardware/software (Win95/Win98) b.) emulated hardware like pcem/86box c.) virtual machines like boxes/virtualbox

do you mean that the game goes into the background if you try to open obs? you should make a display capture and then right click it and choose "edit transform" in the new window set the "bounding box type" to "scale to inner bounds" then set the "bounding box size"to the size you want the capture to be and it will make the screen be as big as it can be inside the bounding box size dimensions