You should perhaps invest in purchasing "VET- Anti Virus" it prevents all of this, it scans and cleans automatically- and auto. Updates , often every 2 hrs or so...
you won't get hte screens saying 'You've been infected with this virus'' etc...
keep scanning...
and also, sometimes pop up adds can come as 'virus' warnings - ignore them... they aren't always actual virius... they are adds for software and anti virus cleaning systems.