No need to worry , you can break the password with XP CD. Please just follow the below given instrucions.
1)Insert Windows XP CD and press start setup
2)Once you get the option to repair the current installation press R button to do so
3)Wait until it reboots (this will happen automatically).
4)After getting reboot you will get a Installing device bar , press SHIFT + F10 to open a command prompt
5)At the prompt either type in "nusrmgr.cpl" w/o quotation and press enter
6)select the users and change or remove their passwords accordingly and apply setting and close the control panel windows and command prompt windows so that setup is running again
The user now should be able to login into windows and there is no need for reinstalling the existing windows.
Hope this helps..