CTD after switching to window mode

Thanks for your reply but the sim ctds without actually starting. I get the opening screens and then it goes to the usual starting , the current still screen, but ctds shortly after.
The sim crashed when I seleceted window screen in game and since then its been kaput.
I normally have very little trouble with the sim.
BTW all of my ctds are crash reboot.
I don’t know if its possible to rest the sim without actually being in it.