to delete old password in laptop

It depends where this password is. For BIOS, @popatim gave you an idea. If you want to delete Windows user, go to Settings, Users, and delete the account (or remove it's password) from there.
 
I have always used the old safe mode trick, but iam not sure if i still exists on windows 8, boot to safe mode f8 or something, that will let you log in as admin and from there you wipe the old passwords from user accounts. to access the data you will need to reassign the data rights which needs admin rights which you should have...