If you've decided to use Avast, there's no need to have Norton on your system. You asked if you 'need to keep norton installed because of the extra things'. The answer is no. I would suggest going to Add/Remove and uninstall all Norton and Symantec entries - to include Live Update if it's there. I don't use Norton, but you might want to also check the Control Panel. Again, anything Norton or Symantec can be removed.
In addition, you can download Norton's Removal Tool. It should help you get rid of anything that's left.
If you're still getting alerts from Avast, after removing Norton, post back. There are other things you can try.
I bought my first computer a year ago and bought and installed the above,which has extras compared to just norton anti virus.The subscription has run out now and I had decided to dowbnload avast instead as i had read good reviews on here.My problem is,when I installed avast it said that there was a norton scanner running and so therefore it had disabled its own scanner as obviously you cannot have 2 anti virus running together.What has confused me is I thought that as my subscription had run out norton would no longer be working on my computer.I understand that it wont update anymore without the subscription renewal,but what exactly is still working on my computer?is it the extra things that come with norton?do i need to keep norton installed because of these,or am I just best to uninstall norton altogether?if so is avast a good complete replacement or do i need something else aswell? i have a few antispyware programmes loaded so am happy with protection for that.i have windows xp,thanks