HELP, i fortgot my laptop password!

Hello,

i forgot my laptop password, and i have tried all the different passwords it could be.
my grandad brought it for my birthday in may, and he's coming to see us in a week...
if he finds out i dont know the password i wont be allowed my laptop anymore..
i downloaded a password resest thing and it never gave me an activation key.
now im stuck.

could you help me please?
thanks, louisa.