Hello Redseujac,
Well, a restart of Windows brought Registry Cleaner window back to the normal (small) size.
And now I found also the way I produced this anormal behaviour.
I opened Registry Cleaner from the main window,
minimized the Settings-window, by clicking on the "Minimize" icon (in the upper right corner).
After finishing some work in a second opened window,
with a right-click on the minimized RC-window I brought up the default Windows context menu,
where I did choose the "Maximize" option instead of "Restore".
So I got the RC-window in full screen, with no possibility - even closing PowerTools - to get back the initial (small) size of the RC-window.
As I said only a restart of Window did the reset.
I am curious if you can reproduce this as well.
Jean-Paul