Ok, Thanx for SuggestMalware Maniac said:What version of Windows do you have Vista or 7?
I would recommend you upgrade Internet Explorer to version 9.
For on demand scanners, correct me if I'm wrong, but isn't Dr. Web CureIt a bootable antivirus. I would recommend Malwarebytes AntiMalware, Emsisoft Emergency Kit, or Hitman Pro.
Do you have add-ons for Chome or Firefox.
If Comodo Firewall won't work for you then try ZoneAlarm Free Firewall.
What Web Browser do you use most?