Slow game startup, log out and exit game

Hello, I installed both mist wow (mini and full), but the game starts (freezes) right at starting the wow.exe, and it can take from 1 sec to 2 mins (or more) to start up, and it does the same at any log out, exit game and server crash. I had to play windowed mode, so the windows (explorer.exe) can be used, in full screen almost the whole computer freezes.
.... back to the freeze, the game just goes all white, or black in full screen, and it doesn't respond.
I watched the processes in windows task manager, and it seems that, the game gets frequently stuck a certain memory that had been loaded, and it has a hard time to get past it, so in short it loads the game somewhat hard in the end.
I tried to delete my "usual" folders everybody is talking about, my drivers up to date, can't say my computer is weak, had weaker computer before worked fine, the problem also persisted without any self installed addons, read plenty wow related similar problems, none seem to change anything.
So, any idea? Ofc, last thing I might try, but certainly not now, is a windows re-install, otherwise I didn't find any other problems.