What DS said!!!
Never even click on one of those things, much less buy from it!!!
You
do need an anti-virus program (if for no other reason than to remove and fix what ever you put on your computer by clicking on the pop-up), but
NOT one that you buy through a pop-up. Look at
Norton or
McAfee. You pay for those, but they are worth it. There are also some freeware programs that can be helpful, such as
Spybot - Search and Destroy or
Ad-Aware (which has a free version as well as version you pay for).
Anyone else know of other good anti-virus/anti-malware programs?