So if you are still getting the pop-ups you are not Viruses or spyware free. You need to run a antispyware combo. Something like
Spybot search and destroy and
Webroot.
Also we need to know a little more about the pop-ups and what they say. Can you be a little more specific about the pop-ups, please?
Note: You need to uninstall Norton before installing any other Antivirus program. Make sure to update the new antivirus and run a full scan in safe mode if posible...
The sfc /scannow should not be done at this point. You need to be viruses and spyware free... Anyways How does it work? simply drop your XP installation CD in the CD Drive. Feel free to close the XP Installation window if it comes up. CLick Start/ Run and type "sfc /scannow" without quotes. Note there is a space in sfc/(space)scannow. do not use or open any application during the process. Once it is finished reboot the computer and see if issues are gonne after login back onto your Windows.
But as I said it is not a good time now for you to attempt to fix any problems you may have. Clean up your system first.
Hope this help