why not use Norton? Quite a few reasons but namely why pay for something when you can get the same or better protection for free?
Other reasons are the amount of resources that Norton (And McAfee use - McAfee is the bigger offender in this regards). BTW resources = 'The amount of RAM memory being used at anyone time'. It is the major reason behind windows crashing or freezing, especially so if you also use Internet explorer and/or any other resource heavy program; i.e. Video editor, Photoshop, Audio editing, all of these are heavy resource users so the more memory you can give them the bet