What should I do? Reinstall? NO!
So how do you recover it? You can’t, BUT you can reset it…
There’s a nifty utility called Offline NT Password & Registry Editor (aka ntpasswd) that will reset Windows NT/2K/XP passwords. It runs from self-booting diskette or CD. Please note that it will not recover AD passwords, and may render EFS encrypted files permanently unreadable.
To save wasting CD’s with small applications you can actually find this utility and a whole range of other useful recovery tools together on the Ultimate Boot CD (aka UBCD).
As if that isn’t enough Winternals (the same people who make Sysinternals Freeware) offer a peice of software called Administrator’s Pak which you can purchase from them. This software creates a bootable CD called ERD Commander which contains a utility called Locksmith which allows you to reset lost passwords.