Boot into Safe Mode and log in as Administrator. Then go to Control Panel into User Accounts and remove your password. Restart after that and your password is removed. You can then add a new password again, but this time, remember it!
I just fixed this exact same problem just 20 minutes ago at one of my coworkers house. So this is very fresh to me.
Oh, didn't know that. You do that at the logon screen? I would assume you have to do it there because you don't know your password to get in anyways. The Safe Mode also works too. It gives the Admin login upon startup.
To change it theres a simple way
But i'm not sure if it will work in your situation
Firstly go to another administrator account which you can log onto on and then go to the account list and then you can remove the password from there and thens et a new one