When I open Firefox, it starts as avg.name,instead of what I set, which is google.

Something is interfering with the set up of Firefox. When I open Firefox, it goes to a URL called AVG.name. When I go to options and change my homepage, it reverts back to that site. When I press enter, it goes to a URL called BTsearch. I thought I could repair it-I even wiped Firefox out completely and re=downloaded the program, but it reverted right back to the same thing. I have done a google search but can't find out much about this. Any help with this annoying problem will be GREATLY appreciated!!! Gary