From another document
here:
Next, Windows Setup will find existing Windows XP installations. You will be asked to repair an existing XP installation, or install a fresh copy of Windows XP.
If no installations are found, then you will not be given the option to repair. This may happen if the data or partition on your drive is too corrupted.
If it's not finding an installation your only option might be to re-install XP. What happened before this problem started?