Me again, sorry.
I've run "sfc /scannow" one more time to reset previously patched files, and it found corrupt files again, but after the restart I was able to see the difference when I changed font color in message box (screenshot1), but without that "aero" look. When I choose default Aero theme I can't see that change (screen2).
Is there another patcher or some other way to do it? I don't know, I'm guessing..
It's annoying, I want a dark theme, but all of them leave black font in message box.
If you or anyone else have any other clue, please help.