Computer viruses....help needed

[MS Fowler]

I have two problems,
1) Affects only MS IE--the home page has been changed to " makemesearch" Its really annoying. I don't appreciate that they can control my homepage, and even if I manually change it, it goes right back to "makemesearch". How do I get rid of it?
2) Affects both Firefox and MSIE--My AVG 6.0, picks up, and dispalys a warning, "trojan horse dialer in windows\system\_T.EXE", but, when I acually run AVG 6.0, it can't find the trojan horse.

I run three programs and none have helped--AVG 6.0, Spybot, and adaware.