Easy way........
10Downingstreet
I had a similar problem....ish
Nosey visitor expected so quick addition of password......then forgot it !!!
Read many ways to sort problem,chose easy one.
1)During start up press F8 to put machine into 'safe mode'
2)Wait until it is up and running
3)Go to user accounts, select admin account delete password, job done.
390
Rather a lazy chap