Just today I finally joined gog (thanks for having me) and download Sanitarium, but following installation I found the game to be in widescreen which has caused the picture to stretch in game. There were no aspect ratio options in the installation process, nor are there settings in screen options within the game. How to I reinstate the original 4:3 aspect ratio?

Problem resolved - I just had to change the aspect on my TV from wide to normal - DERP. I would remove the topic, but it appears I can't. Thanks for reading and I hope it at least assists others.

No need to remove it, might help someone. ;)

While it may be possible for people who use modern TVs for display devices to switch between aspect ratios at the push of a button, people who are using computer monitors may not be able to force the aspect ratio on the display itself. For nVidia users you can open the "NVIDIA Control Panel" and go to Display >> Adjust desktop size and position. There you can force the GPU to scale to aspect ratio rather than full screen. This means a 4:3 resolution like 640x480 or 800x600 will render with the correct aspect ratio with black spaces to the left and right of the screen, assuming your monitor and desktop resolution is wide, of course.

For most purposes you can leave it at this setting permanently, though you should be aware of that many computer monitors are 16:10 while TVs are 16:9, so if you pick an inappropriate widescreen resolution you may get a few pixels of black bars at the top and bottom of the screen (say, forcing a game that is running at a 16:9 ratio to scale properly on a 16:10 desktop resolution).

Does anyone know how to achieve this, if neither your display nor your GPU has the "pillarbox" option built in?