No format needed! this can be fixed, to start with delete all your temp. files, and temp. internet files.
Remember your pass words for any sites that need them, (Such as this one), and then delete all your cookies. This will help to get rid of anything on your drive that should not be there, without causing any major changes.
If you still have the problem then download Ad-aware from lavasoft. com
Download it anyway, it's a good free program for clearing out any spyware that has loaded itself onto you drive. click here when you have done this it will be a good idea to give your H/drive a defrag, and you will find your PC will run faster on and off the net.
If you are still having problems, please post back on this same thread for more information. J.