How to remove Key/Activation

Hi.. I just bought a used computer from a friend.. He had Norton Internet Security 2011 installed.

I bought a new key and tried to uninstall and reinstall NIS to use my key (tried with the removal tool also)

But I still have his activation.. And if I click on "account" in NIS.. A page loads to login.. But it's showing his email addy

How can I remove all traces of his account.. Only option I see is to renew.. I don't want to renew his subscription