Free AVG is certainly good enough, IMO. And, reading through these forums, it gives a lot less problems than the two other programs you mention!
Download it from www.grisoft.com.
Note that it's a bad idea to have to competing products active at the same time. So completely uninstall Norton before installing AVG.
My Norton antivirus program is ready to expire soon and I have been told of a free antivirus system (AVG) available for home computers. Just wondering if such a free system is effective in stopping posible virus assults or would one be wise to invest in a system such as Norton or McAfee. Any advice would be welcomed.