I had this happen to me recently
I resolved it by:
1.Going off line.
2.Running Ad-Aware,although it removed the malicious spyware it wouldn't remove the browser hijacker.
3.In IE6 I went to internet options and deleted all cookies,files and history.
4.Still no luck so I used system restore and that worked,after restoring I turned system restore off(to remove all traces),rebooted and turned it back on.