Found this today. Didn’t try this myself but seems very useful. It looks like your computer password can be reset by opening your operating system in safe mode by pressing F8 and then changing your password. Problem solved!
Forgot your computer password? Boot up in safe mode (F8 during startup), log in as administrator and then change your password.
— Life Tips (@LifeTipsEasy) April 3, 2014
Once my son changed password on desktop computer and then wasn’t sure what was that. Luckily we could guess it at the time. Now I am not afraid of similar situations anymore!