The Steam version is v1.3 or v1.5, and you can no longer apply the v1.4 update to the v1.3 file, due to Steam licensing restrictions. However, the v1.3 should still play fine, even in Windows 10. There are a few "tweaks" you need to do on the executable file though.
First of all, make certain that you installed the "DirectX v9.0c" and its associated Windows Media files. If you have to, run the Steam installer for SH4 again, and be certain that you choose those from the menu, which comes up after the user's agreement, the language choice and the path to install to (as mentioned, change that to something other than Program Files):
This is a screen grab from my disk version of v1.5 install, so the Steam v1.3 might be a little bit different, but not much. Do not bother with GameShadow, and you probably don't need that 11 year old+ version of Acrobat Reader. GameShadow shouldn't be on the Steam menu, if I remember correctly...
After you have the game installed, go into the Steam Library folder where you put the game (Steam can stay in Program Files, but the game cannot), and select the SH4.exe file. I have Steam on my Win10 laptop in a "Games" folder, such that I go to "C:\Games \Steam \SteamApps \common \SH4\", of which I had also renamed the default "Silent Hunter Wolves of the Pacific" folder to "SH4". Right-click on the executable SH4.exe, and choose "Properties" from the menu with a left-click, then "Compatibility", and click the "Run this program in compatibility mode for", then choose anything from WinXP (SP3) through Windows 7. You could also click the "Run this program as administrator", which would be influenced by how you have the UAC (User Access Control) set-up in Windows. Try it without if you want to, but you might have to come back in. While there anyway, on the "General" tab, make certain that the "Read-only" box toward the bottom of that tab is cleared.
The reason for that last, is so that you can use LAA (Large Address Aware) if you have a 64-bit version of Windows (Win10 usually is) and more than four gig of RAM. That will give the app more room to breathe. Read up on LAA in CapnScurvy's thread
Windows10; Large Address Aware; SH4 Install. For those with other Windows 64-bit OSes, it can still be used, from Vista through Win10...
