Acer aspire one. user id and password problem

Hello,

iv been given a notebook for my daughter.i want to fix it for xmas but im out of touch of windows xp.
when i turn on the nb it goes to the user log in page, and the name inthe box says user...then b4 i type anything it says
THE SYSTEM COULD NOT LOG YOU ON.MAKE SURE YOUR USER NAME AND DOMAIN ARE CORRECT,THEN TYPE YOUR PASSWORD AGAIN.

i understand it hasnt got a cd drive so im stuck there and lots of posts i read say click start and..... but i cant get to that point.
the girl who gave me the nb gave me 3 diff user names and one password. an it isnt any of them. is there anything i can do to save me going to a shop. i have two months to try an fix it.

i really hope someone can help me. thanks for reading