Starting a new Antivirus 2012 subscription with disc.

My current subscription expires sometime today. I always renew with a newly bought Antivirus (sealed) disc.

Last year, I tried to renew by simply loading the disc, but the next 365 days of Norton didn't register. I had to deal with Norton on the phone, which was a long hassle, to be credited with those 365 days.

What should I do today? Wait until my subscription runs out sometime today? Or remove Norton completely from my PC and start again with my new disc?

Thanks in advance.