If you have forgotten your administrator password, you don't need to reinstall ......
Here's the solution of it....

Goto http://pogostick.net/~pnh/ntpasswd/

Download the Boot Disk from this site

that will let you reset the password of any account on NT4, Windows2000 or XP.

Just follow all the default settings which are for the admin account. Used it many
times with great success.

They also have a bootable CD image you can download.