Delete the Save folder, which defaults to C:\Users \UserName \Documents \SH3 or similar. The game will rebuild the data when you first start SH3.exe again. Also, SH3.exe Properties also has to have Admin rights set, and you should set it to Compatibility mode, of which most anything from Windows XP SP-2 through Windows 7 works. You might also have to Disable Fullscreen Optimizations, and possibly set Change DPI to Application. It is recommended you use MultiSH3 to set a new Save folder with a 3 character name of your own choosing. But KC is NOT backwards compatible with anything.
Edit: If you keep having issues SwissSubCommander, run JSGME, then click on the "Tasks..." link in the middle of it. Choose "Export activated mods list to..." and then choose either "Clipboard" to paste it into your next posting, or "Text file" to copy and paste it later. We want to see the "path" of your install. Also, if you would list what cpu your computer has, the amount of RAM, and what your video card is please... Thanks