Indrajit,
The easiest way to release a password lock in non-trusted system , is to use SAM, SAM ==> Accounts ==> Users & Groups , choose the User and go to action field and choos "Re-activate user" ,
You can also release by replacing the * in the password file of that user with null value, but that will be insecure.
Cheers,
Raj.
" If u think u can , If u think u cannot , - You are always Right . "