Did you forget your password then don't worry. I am going you to tell the process you to recover password without formatting windows i.e without loosing your data.You can recover it by trying the simple steps given below
Step One
Open command prompt .You can search in start menu ( run as an administrator)
Step Two
type net user it will show administrative name.
(suppose user name shown is dell)
Step Three
then type net user dell computer (computer is my new password)
Your password is sucessfully changed without knowning old password