Hi merry,
Norton antivirus is very well known anti-virus.But according to me it is not good like others and make your computer system too slow and the update file size is too large.I had used NAV one time.After installation whenever I started to update the file,saw that 100 MB data have been used to update.So can you imagine?
Many anti-virus I have used before such as Avira,AVG,Kaspersky.Avira antivirus is a vert good quality of antivirus.It don't make your system too slow and must get a good response.The rest of two are average type and and make your system quite slow.
At present I am using Avast anti-virus.It is very high quality of performance and you can get it free for one year.So,I personally recommend you to use Avira anti-virus.
Regards,
Priyabrata Das
"Be Honest to You, not to others"