You need to run it in fullscreen and tell your GPU driver to stretch it to aspect ratio.

This has been a solved problem for like 10 years.

Is there a way to do this for specific games, or is it something that needs enabling and disabling every time?
I use Nvidia for reference.
*Update* I messed with the settings, changing the "Perform scaling on..." option from display to GPU triggered the change, i guess that's what you were suggesting, thanks for the help i didn't know it was possible.

Used both, same result. I can see it to windowed full screen, but pressing the wrong button also causes the menu to open.

Weirdly, yesterday after I installed the add on I had higher resolution options than 640x480, but when I played today they were gone.

EDIT: Ok, for some reason my install of the add on/jazz 2 plus seemed to "fall off". I re-installed (You can tell from the title screen, if it has art of jazz, spaz and the yellow on on surfboards, you haven't installed the add on yet.) it and when the game itself started, it was on the highest resolution and in full screen.

So I'm guessing the base Jazz 2 for whatever reason doesn't allow a proper fullscreen. Odd, lol.

How do we do that? I tried the NVIDIA control panel and it has nothing regarding stretching to fit the aspect ratio. Am I looking in the wrong menu?

What settings? The in-game ones don't have scaling options and there are no GOG graphics options in the game files. How do I change the scaling options like you did?

My Nvidia control panel does not have a display option: It just has 3D settings and nothing else. That's because my laptop monitor is connected to the main CPU and not my Nvidia GPU. I looked up a solution to that problem and apparently adding a new monitor to my HDMI port (if I even have one) will fix it.

https://forums.geforce.com/default/topic/496259/no-39-display-39-tab-in-nvidia-control-panel-/ (bottom post by NVidia tech support)

That's all well and good but:

A. I don't have a second monitor

B. I don't need one nor want one

C. I don't have space for one anyway

Is there another way I can alter the display settings in Nvidia for this game without wasting my money on a display device I don't need?

That thread is about Nvidia Optimus laptops and have two replies suggesting owners of Nvidia Optimus laptops should change scaling options in their Intel driver options instead. Have you tried that?

There are three software based scaling correction programs that can fix aspect ratio on this game (dgVoodoo2, DXGL, DxWnd), but they are all more complicated to use than changing your driver settings.

I couldn't get the intel options to appear when switching display drivers so I'll try dgvoodoo as that worked for Tomb Raider 2.

Just installed GOG versions (JJ2+Crhistmas+JJ2+), made custom resolution (nvidia or CRU) 640x360, it appeared in game, its 16:9 and it doesnt look too weird/sctrech etc (never seen jazz in 16:9 so it may look weird lol. (i have gpu scaling on with keep aspect ratio and ticked replace in-game scaling and scaling option high quality in nvidia inspector.)