Sory, but I can't take your word on the ownership. Even if you are totaly honest, other that may be less than honest could use this information to unlock stolen laptops.
If there are more than one accounts, log into another one for whitch you still remember the password. Make sure that the alternative account have admistrative privileges.
From an administrative account, you can reset the password for any other account.
If you don't have any alternative account set, you need to go to some computer shop with some solid proof that it's realy your computer.
If the computer is to old and you no longer have the receipt, a list of some content may do the trick, but that content can't be obvious in any way.
They can then do a password reset.
It will cost you some $.
Now, whenever you change the password in the future, it's a good idea to keep some record of the new password in a secure place that's NOT just next to where the computer is normaly used.
Electro, July 2013