click on the the start button. then click on "run". enter this "notepad.exe c:\windows\system32\drivers\etc\hosts" without the quotes (->"<- these things).
press enter. this is your hosts file. look at the post above and remove anything that is diferent then that post. this is the result of addware. to remove things like this, you need to get a copy of a program like "adaware".
http://www.lavasoft.de/