We were reccomended a product called AVG by a Microsoft employee, it is free for home use as they make their money through their business arm. It has been good as gold to date, they don't even put you on mailing lists, or send pop-ups.
It's well worth a look even if you only try it whilst looking for an alternative.
Their home PC website with the link to the Free version is http://free.avg.com
The download you want (there are several options) is at the top left. In the UK, the link is http://free.avg.com/gb-en/download-avg-anti-virus-free
, so presumably yours will be similar.
Hope you find it helps,
Alan & Katrina
Last Cruise: Queen Victoria November 2014
Next: Queen Elizabeth December 2014
Followed by: Minerva April 2015
Golden, Grand(2), Caribbean, Sea(4+1 aborted)
Adonia(4+2), Arcadia, Artemis(2), Aurora(5), Azura(2), Oceana(3), Oriana(11), Ventura(2), Victoria(5)
QM2(2), QE2(9), QV(6), QE, Caronia(2), Minerva II, Fred.Olsen(8), NCL Jade, =X= Eclipse, HAL Ryndam, Aza.Journey