Problem re-installing norton after resetting computer to factory setting

Hi 

I have just re-set my 2008 windows vista home premium computer to the original factory settings and then installed all the windows updates again

including service pack 1. But when trying to re-install norton it is coming up with an error saying that my version of windows is incompatible with

norton but everything is installed that norton is saying it needs . what am i doing wrong .

please help.