Thanks a lot friends....It really worked for me. I faced trouble because of the dll named pmnkkjg. I never felt hard debugging when compare to this crap. At last ur clue helped to delete that guy from system32. It camofulaged itself as THotKey.exe and popups came whenever I invoked IE.

regarding steps to revoke permission, juz rt click and go to security and deny the permissions and also click on advanced button in the security screen...