"Forgot your Windows NT/2k/XP/Vista admin password?
Reinstall? Oh no... But not any more...

"chntpw is a utility to (re)set the password of any user that has a
valid (local) account on your Windows NT/2k/XP/Vista etc system.
You do not need to know the old password to set a new one.
It works offline, that is, you have to shutdown your computer and
boot off a floppydisk or CD or another system.
Will detect and offer to unlock locked or disabled out user accounts!
There is also a registry editor and other registry utilities that
works under linux/unix, and can be used for other things than
password editing."