Take a look at the
FREEWARE page and use the Anti-Trojan programs. (I use AVG Free Home Edition too and it is usually excellent.)
At the top of the page (scroll up) you'll find an on-line scanner.
I added the Google Search bar to IE to stop pop-ups and made sure that these two entries are dealt with...
In IE, Tools, IE Options, Advanced, & under "Navigation" Uncheck:
"Activate install on demand" [Other] , and, "Activate install on demand" [Internet Explorer]