Apparently there is no way of setting/configuring a windows position on the screen. I couldn’t find a place to define X and Y or top and left. There is however a function, if you write your own application in C++(SetWindowPos). Also deleting
[-HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\BagMRU] and the like didn’t work for me, especially since the (current) user, wasn’t allowed to use regedit.
Thanks to paradroid on superuser.com, I found another, reasonably usable solution: Hold down CTRL while clicking on the [X]-button of a window. Windows will then remember the position for the next start.