non upgradeable OS

I have a student version of windows XP pro on my new computer – it will not let me update the windows service pack. so – i bought a new version of windows XP Pro. when i tried to install the new version it tells me that the version i have is not upgrade able and will not let me install the new version. When i try to change the apps installed on my machine and put in the new code # it tells me that it is incorrect because it has the old number on file internally. – is there any way to upgrade my system without doing a complete format and starting over