Malbeorht a 7 f

http://www.topeven.com/story.php?id=170426&PHPSESSID=de24aacc3d69425cf2c9f4b5475fb2dc
I have been running the free version of AVG for years but it has been causing problems with Internet Explorer 8. I solved it by replacing my AVG with BT Net Protect but now my father is having the same problem and his ISP doesn’t provide any security software. I want to uninstall AVG from his PC but I’m not sure what to replace it with. Does anyone have any experience of other free anti-virus software that they can recommend? Many thanks.