Spybot Search and Destroy might be able to find that adware you're having trouble finding. Spybot is a dedicated ad remover, and I recommend it highly to you if you're having problems with pop ups.
Another thing to prevent some pop ups is to go into your control panel > administrative tools > services. Disable and stop the service called "Messenger." It will not affect your internet browsing or instant messaging in any way, and I find it a vulnerability when you allow it to run. A fair amount of ads rely on this service to gain access to your computer.