4.2 What do I do if I have problems with my mouse buttons?

Emacs assigns bindings assuming a three button mouse. On Windows, if a two button mouse is detected, a hack is enabled which lets you simulate the third button by pressing both mouse buttons simultaneously. w32-mouse-button-tolerance defines the timeout for what is considered “simultaneous”. You can check how many buttons Emacs thinks your mouse has with C-h v w32-num-mouse-buttons.

If you find yourself needing the mouse-3 bindings more often than mouse-2, you can swap the buttons with the following code in your init file:

(setq w32-swap-mouse-buttons t)