First off, you mention "steammapps common, sh4", but don't say where that is. It is important to NOT be in a Program Files folder with SH4 on a 'modern' Windows OS. Using a Steam game, there are some caveats to moving the Steam Library out of there, if needed. Consult Steam's Knowledgebase Article "
Moving a Steam Installation and Games for more info. That will take a while to do, and the more games, the longer it takes. Windows is the problem if you are in that "C:\Program Files (x86)\Steam" folder, since it "protects" the user from themself, by not allowing "un-authorized" alterations to what it considers "system" folders, such as Program Files. To be "authorized", the app has to be written to at least the Windows Vista GUI, and SH4 and JSGME are both Windows XP.
2nd thing with the Steam version and v1.5 Uboats add-on, are you landing in the correct folder when attempting to activate the mod? I do not have an SH4 Steam game, so I am not familiar with how that works. FotRSU is not compatible with v1.3 of the game (the base Steam version), so you have to be in the Uboats v1.5 folder.
How many single mission choices do you get in the menu? If you have a lot, like four times the number of stock, then that portion of the mod is seemingly activated OK. However, the Single Mission portion of the game does not load all of the Career files, so needs less RAM to run them, and your computer has enough muscle to get through the ones you have tried. In the "Extras" folder, you will find "laa_2_0_4_NetFramework_4_5.zip", which you should be able to use. It has a netFramwork gui. But "laa_2_0_4.zip" works fine also. Any 4gig app of that type is fine. They all do the same thing of flipping some bits in the SH4.exe file's header that then signifies to Windows that the app is capable of addressing more RAM. By default, the program was written to that spec, but most computers back in the Windows XP days had 32-bit OSes. Take one of those zip files, and drop it in the root folder of your game, where Data, Extras, Support and other files are, and extract that there. Run the resulting "Large Address Aware2_0_4.exe" (or similar) file, and use the "Browse" dialog button (shaped like [...] ). Make certain that you are in the correct folder, and choose the "SH4.exe" file. Put a tick mark in the box next to "2.", which should then populate that portion, which then activates the "Save" button. The deed is done. That is, ~if~ your SH4.exe is writable... so maybe the first step for this should be to find your "SH4.exe" file in the game folder, right-click on it, choose 'Properties' from that context menu, and on that 'General' tab, under the 'Attributes' section, make certain that little "Read-only" tick box is empty. OK your way out, and then do the LAA stuff. The game should run much better now...
