I don't know.
I tried running in on my new Windows 11 computer.
It runs fine, just no sound and my sub just sits there at flank speed and 5k time dilation.
Not playable.

works fine on windows 11

I can't get it to launch on win 11

It was running on win 11, but some update has caused it to stop working within the last 6 months, any idea what update caused the problem?

U need to go to steam, go to library, right click on the game, properties, installed files, browse, find the sh4 with sub icon highlight it (left click once) then right click, properties, compatability, run on windows xp (servie pack 3), then load game.