I wish to install Windows

Question

I wish to install Windows Vista Home Premium. I already have Windows XP. I pay for Norton Internet Security by direct debit through Tiscali and have done so since, 2006.I have run Norton Liveupdate. Windows still say that I must uninstall Norton Security before upgrading to Windows Vista and I will not be able to reinstall Norton Internet Security because of compatability issues. Can you help me,please.