Hi Jane
Little footnote from a newcomer here, another "Norton resource hog hater".
I, too, use AVG + ZA but there are other (free) protection tools you would be well advised to add to your protection barriers.
I agree Avast is also top notch.
Read this handy little guide for what you need to help keep your computer free of malware ...
http://www.help2go.com/Tutorials/Pro...Hijackers.html
[You have already done steps 7 & 8]
The guide has all the download links too so you just "click & install".
Hope it helps.
OJ