It depends on your OS too. If you use windows XP, you can easily get an XP password cracker on Google. I don't know whether there are tools for Winows 7 yet. you can have a try and tell us your findings.
Did you search online for any solution? It is easy to find cracks in Google.
You are right because today mostly all things and all solution we can find on google so try to search in google. It may be help you. In other way I will find it from my friend.
If running Windows then, start your computer in safe mode by pressing F11(or relevant function key) before the windows logo shows up and starts loading. When you start your computer in safe mode it has an admin account that anyone can use. I don't know if you can change your password without knowing your old one but you can create a new admin account and delete the old one while saving the files.