How to Recover/Reset Windows NT/2000/XT/Vista Password Using Ubuntu Live CD

Open a terminal
$ apt-get install chntpw
Chntpw is a program designed to overwrite Windows NT/2000/XP/Vista SAM password.
Mount your Windows partition with read/write support
Then you need to locate (use your Command line Skills) SAM file which for Windows 2000 and XP is normally located at windows/system32/config or winnt/system32/config.
Once inside the ‘config’ folder , issue this command:
$ sudo chntpw -h for help
$sudo chntpw -l SAM for list of windows users
$sudo chntpw -u USERNAME SAM for reset password
It is recomended to reset the password to BLANK. Source: shibuvarkala.blogspot.com