hi .. u can change ur window's password
without using old password
just follow these teps::
1)go to:: run
2)type :: cmd
3)cmd will open and u will get
c:\user\indrajit> by default and dont do
anything just follow next step
(here (indrajit) is example.. u will get ur name)

after type:: net user "name of addministrator" *
and it will ask for direct new password

example::net user indrajit *
enjoyyyyyy