Be very careful, last week this happened to me, but it wasn't actually avg just a good convincing copy and it beggared up my computer which then had to go off to be mended.
Hi, I had AVG 7 which was fine but then they "improved" it with Avg 8 which gave me all sorts of opening and closing down problems. I uninstalled it and computer was immediately ok. I now have Antivir PE Classic which is also free and great, try it