Myself, I wish that the developer of this extremely helpful application had
picked a different name.
HijackThis is an application which helps with the guided removal of possibly
unknown spyware or trojans or viruses from systems.
Microsoft Antispyware does repair some browser hijacks, but probably not
all.
If it is identifying yours, but not succeeding in removing it, please try
that same operation in safe mode.
If it doesn't identify that your browser is hijacked, please submit a Tools,
suspected spyware report, and mention what URL the browser is taken to.
Then go to the forum the Plun references and see whether, with the help of
HijackThis, the experts there can help you get this cleared up.