dosbox is a regular windows application, so if it can have THAT effect to
an operating system your OS/drivers are seriously messed up, don't you think?

Actually now I made a notice that it seems to happen always when pressing alt or a combination including the alt key. And if you press the left alt key, it flips the screen left and the alt gr flips it to right if you know what I mean..

Nice 😀
Maybe you have some background app/windows feature active that flips
the screen? As i can't think of anything in dosbox/sdl that would do that.

Yeah 😜 The only thing I can make up is that it leaves the colour scheme and game settings on.etc??Although I dont know how it would be possible. The mouse cursor is fucked up too, so it inverts and moves sluggish..

Well no idea about that, disconnect from the internet, then kill a few background
apps and see if you still can produce that effect. Reboot if finished testing.

Also check your graphics card drivers/directx version, and keep an eye on
the dosbox console window for notices.

Hmmh. It seems to work fine now.. I didnt even do anything special.. I logged in with the "faulty" account and some icons where shitty again but some where ok, then restarted and its like nothing happened. Strange..