The default Chimera middle mouse button assignment of XY-translation may not work on Windows systems using Logitech MouseWare. The middle mouse button is set to perform autoscrolling and does not get reassigned automatically to XY-translation within Chimera. To make the middle mouse button work with Chimera, it is necessary to adjust the mouse setup: clicking the mouse icon on the Windows Taskbar brings up a Mouse Properties widget. The Quick Setup panel is in front, showing that mouse button 2 (the middle mouse button) is set to AutoScroll. Clicking the Buttons panel brings it to the forefront and then clicking Options... opens another widget. Clicking the AutoScroll tab then reveals a checkbox marked Use Office97 Compatible Scroll Only. Activating this checkbox should solve the problem.