1. Options - Keyboard/Mouse - tab Keyboard/Mouse - group of settings Mouse - set Right button to "Make selection".
2. Take two images big enough to cover most of your Viewer window and place them in some folder.
3. Open first of them in XnView Viewer mode. Make sure that is opened first so that another image is next.
4. Right-click first opened picture somewhere near its top left corner to pop up menu. Notice small square appearing at the point of click which marks beginning of selection.
5. Choose from menu "Move to folder". When appears window titled "Move", move window itself closer to picture's bottom right corner.
6. Pick some another directory for picture destination and click button "Move".
When moving is complete and Viewer loads next picture, notice rectangle of area selection from the point of click for calling menu to the point where you clicked on button "Move".