Let's do this then, and point you at CapnScurvy's
Windows10; Large Address Aware; SH4 Install thread. He had just gotten himself a new computer and installed Windows 10 on it, and Silent Hunter 4. You might be putting the game into "Program Files (x86)", which can cause issues, since Windows "protects" that folder and doesn't allow certain changes to take place. The Capn also discusses the use of LAA, which allows the SH4.exe to use more than 2 gig of RAM. Try reading through that and following his advice there...