Go to mouse settings. There will be a control invert mouse (on/off). Click the button inversion. In exactly the same way is possible to enable the inversion, adjusting it along the axes X and Y (move the relevant sliders to the right). Invert mouse autumn comfortable for computer games, but not in normal operation.
If in the control panel in the mouse settings, nothing like that was found, click "start" then "Run" (or win+r) and type there regedit. Find a way HKEY_CURRENT_USERControl PanelMouse and look at the value SwapMouseButtons. If there is 1, then change the value to 0, then the inversion will not.
If the inversion came out of nowhere, then do a system rollback back (backup) at a time when, in your opinion, inversion was not.
Try uninstalling the mouse via the Manager. Then clean the registry Ccleaner or something stronger. Restart the computer and connect/install the mouse again. Then she must earn a "clean slate" and without any inversion.
Download and reinstall the driver for your mouse. Also, the problem may be actually the simplest – if you have a wireless mouse, it could just simply sit down batteries, which will affect the correctness of its work. In this case, the occurrence of undesirable inversion. Change the batteries and test the controller.
Go to start menu/settings/control panel. There select the Mouse tab and Buttons. It is possible that there is a tick near the item "left-handed". If it is there, check the box next to "righties", and the inversion will disappear (or Vice versa if you're left-handed). In some games there is a special function to disable inversion. Go to the menu item controller and select invert → disable.