remove linux and dual boot loader from windows XP machine.
remove particion -> windows XP, my computer, manage, disk management
*Make sure* the windows XP partition is *active*
boot up XP disk: recovery console , fixmbr. This requires the administrator password already setup.

by the way

To set administrator password -> windows XP, my computer right click, manage, user account etc.,,
..or. if your XP does not show user account there…
boot windows in the safe mode (hit F8 while booting up) in safe mode welcome screen, there is a login for “administrator” which is not there in normal mode.
the password for “administrator” is usually blank, so there is no need to enter any password there. login, then go to manage account page in the control panel. you set up the password for administrator right there. Once done, reboot and use the XP disk, hit R for recovery console, select the Windows you want to logon (usually there is one and only one choice) and use the password you just set up.