McAfee Security Centre

I bought a XPS15 laptop. It was pre-installed with McAfee Security Centre for 30 days. I want to renew the same for my laptop, but it is having higher cost than that available from Dell (if subscribed for 15 months). What is the difference between McAfee Security Centre and McAfee Total Protection 2012? Can I replace the existing McAfee Security Centre with McAfee Total Protection 2012 if yes, how? Please reply. Any comment will be highly appreciated.