How you I get rid of an ad pop up on my Computer?

It's called an Ad Rotator. The window would pop up with different ads from companies like target, tmobile and other wedsites. My security company can't seen to help. My spyware deletes it everyday but it comes back even if am online or not. I do have DSL so I understand I'm always online, but this thing pops up if am use excel or something.