Winantivirus Pop up when i get ot the login page

almost every time i get to the login page, i get the same pop up.  i have norton antivirus on my computer, and the popup is for WinantiVirus.  once i close out of that, norton pops up saying  i have a virus on my computer.  i now know from running multiple virus scans on the whole computer that the virus isnt there.  i also just clicked something about the "virus" and read that it is something that exaggerates the risk of it, cause norton says high alert.  it tries to get you to download winantivirus i guess.  i am wondering if im the only one with this problem, because it happens on both my computers