Is there a way to run this game windowed? I am on an ultrawide monitor and this game looks just awful stretch from 4:3 to 21:9

I haven't found a way to force the game to go into windowed, though a 4:3 resolution should work. If it still gets stretched there might be a scaling option in your monitor itself that needs to be adjusted. I have multiple monitors and my second monitor gets offset to the side because of the low resolution so windowed would be perfect.

you can wrap the game using dgvoodo or similar tools. though if you do so, and want to submit a run, you must double check that the games internal frame rate (FRTE) is still 59/60 using the trainer form the resources section.

http://dege.freeweb.hu/dgVoodoo2.html

edit: and yes talic is correct, your nvidia/ati drivers should have a scaling option for non native resolutions.