How did your computer last become infected with a virus? did it install without asking you first? or did it change a load of settings you couldn’t undo? if yes to any of these then it was probably because you were logged-in with administrator privilege.
To mitigate against unwanted changes to your PC – always use a non-Administrator account. Set-up an alternative account with administrator rights and assign it a password such that you always get asked for a password before critical changes are made to your machine – thus allowing you to ask yourself “did i really ask it to change something critical or permanent?”, if not then cancel out of it and prevent it from happening.
Privilege separation is a key aspect to computer security, even the most secure of systems can be made insecure by badly coded programs allowing unprivileged users to modify critical files and settings.
It is too easy to “just-click-yes” and then go oops afterwards, this provides a nice barrier for unwanted and unauthorised changes.