Windows activation

Hello,
I've got windows xp pro uploaded on my laptop and it wants me to do the windows activaion when i do that does it regster the copy of windows to that computer or would i still have to regster the copy cause the copy i am using is from a premade i had that was junk, so i wanted to know if i go to activate it if its going to error or say that this product is in use or somthing. any help plz