Password problem

Hi
I down loaded wubi and then ubuntu ,done a reboot came to the main screen needed to entry the password , but when I entry a pass word that I entered at the down load stage it tells me this is wrong, now how can i check this password or clear it because it will not let me do anything, this down load is on a xp pc also if I UN-install is there a possibility that this password shall still be there

many thanks for any help
                                              Hugh