Malwarebytes Anti Malware, Spybot Search and Destroy, Combofix and SDFix, as well as an AVG scan should clean most anything you've got up.
I usually start with a hijackthis log, and work from there. If there appears to be something particularly nasty, extract SDFix to the systemroot drive (usually C

, reboot into safe mode, run SDFix, reboot, run combofix, reboot, run a full MBAM scan, reboot and run it again and see if anything re-appears, reboot and run spybot S&D, reboot and run AVG full scan.
That generally gets rid of everything "naughty".
I run no antivirus on any of my machines, though, and the last time I bothered to run a scan with MBAM and Spybot, it found nothing.
Enable automatic updates through MS, don't use IE, and don't download/install suspect applications, and you've got nothing to worry about, for the most part. At least nothing that will be fixed by using Norton.
IMO, almost all of the "for pay" antiviruses are pretty much a waste of money. The only one I'd probably really pay for is F-Secure.