Laptop user problem

Question

i bought a laptop from hp and it had to be sent back because hp had forgot to install wireless 5 days later it came back and i turned it on to find another user made. this was not a problem because i put a password on the user i made before i sent it back. hp have made both users administrator. i have tryed deleteing one of the users but i cant. is there a way you know of that i can delete one of the users?

replies much appreciated