So, let me get this straight. You have version 1.3 of SH4 on a DVD disc? It's
not a download coming from Steam...right?
You have installed SH4 into your "Programs (x86)" folder? Although I don't think you should have done that......but, you may wish to look at
this thread, it has to do with installing SHIII onto a Win 8.1 computer.
The two things you should get out of reading this thread is:
1. If you have installed the game into the Programs (x86) folder, run the game as "Administrator".
2. Run the game in "Compatibility Mod" which forces the computer to run the game in an alternative OS, other than Win8.1.
Much like what Portugeezer so correctly stated........by right clicking the .exe file (I'm talking about the true .exe application found in the Silent Hunter Wolves of the Pacific folder....NOT the .exe "short cut" file on your desktop. You may need to make another "short cut" IF you make changes to the .exe file as noted) you will find the menu pages as described under the "Properties" tab.
Also, under the "General" tab of the "Properties" menu, of the games true .exe file, make sure the "Attributes" section DOES NOT have a checkmark in the "Read-Only" box. Having it checkmarked, you can't change a thing in the other tabs.
The main reason I asked about which version of the game you have is because version 1.0 (the first release) required you to have the DVD disc in the DVD Drive before it would start, due to the games protection from piracy features. Some time later, in a patched updated version (either 1.3, or 1.4), the requirement to have the DVD in the Drive was dropped. I just don't remember when the requirement was removed.