Your PC has been jacked...
try a system restore go back a few weeks if you can..
try removing spyware (etc..) in safe mode well unplugged from the internet..
you can also try
http://www.killertechtips.com/2008/0...ithout-addons/
IE in safe mode (turns off all addons)
But I'm guessing you are going to need to move your files to a backup drive and format C..