Emission Systems For Cars And Trucks Cheapest Parts On the Web

My girlfriend has been made redundant and her employers told her to take a laptop as it would only go to administrators. Anyway it is locked up to the max with only one username, password and domain that can access it, however she wants to make it her own. Everyone i have asked has said the best thing for me 2 do is flatten it and install a new operating system. I was going to use Ubuntu for a change as its free but as iv only been studying i.t for 6 months i dont want to screw it up. So my question is how do i go about wiping it so i can just install Ubuntu and set up all new user accounts so she can use it?

Notes. . .

it currently runs windows xp
you can not add any other administrators
you can not edit the existing account or change the name or password to her own

cheers
I dont have any CD's i just have the laptop and nothing else