Sometimes it happen … a new installation finished and the menu box is created outside of the screen where it can be reached via mouse, so you couldn´t click on the resize button. You can kill the windows now with task manager but there is a better way.
Select the windows so that it has the focus with:
"alt" and "tab"
After the windows has the focus press:
"alt" and "space"
then select move with the cursors and move the windows to the focus with the cursor keys.