What can cause the screen image on a laptop to turn upside down ?

The screen image on my wife`s laptop was upside down yesterday. The only thing I could think of was to do a system restore and this solved the problem.
Tonight she has switched on and the same thing has happened. Can anyone explain( in layman`s terms) why this is happening and how it can be cured ?

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).