What you might be running into is the video properties of the SH4.exe file not cooperating with a newer computer. From your Steam menu, you'll want to go to the local files folder, or go into "C:\Program Files (x86) \Steam \common \steamapps \Silent Hunter Wolves of the Pacific" (assuming a default install) and find the SH4.exe file. If you don't see the ".exe" portion of the path, then click on the first-listed SH4 file. Right-click on it with your mouse, and choose "Properties" toward the bottom of that menu. Then you'll have to start experimenting with the settings on the "Compatibility" tab of that pop-up window, as below, which also shows the "Change high DPI settings" window:
Next thing, if that is where your Silent Hunter Wolves of the Pacific folder is, you'll have to move it to where it is outside of either of the "Program Files" folders, and also outside of any other of the several Windows "protected" folders. If you have a valid 2nd hard drive (or SSD), then you can install a 2nd Steam Library folder on it, and put SH4 over there. Consult the Steam Knowledge Base article
Moving a Steam Installation and Games as appropriate, for more information. I have my old DirectX v9 Steam games in "C:\Games \ Steam..." on the one computer, and "F:\Games \Steam..." on another, with the "Games" folder being one that I created. Windows User Access Control (UAC), among other technologies will prevent JSGME from properly activating a mod if you keep it in a "Program Files" folder, since neither SH4 nor JSGME are 'registered' programs in the Win database. Not that they are "bad" programs, just that they were written to the WinXP interface, not the Win Vista and later paradigm. As such, Windows will rollback all edits done to cfg and other similar files, resulting in a partial activation of a mod, and then you end up with a mess of a game...