There are two types of pop-up. The first is (usually unwanted) web pages which are sent to your PC when you visit a particular site. (i.e. if you don't visit those sites you won't see any pop-ups). Pop-up programs generally do a good job of blocking them (although it's probably better to just use a decent browser, such as Firefox, which removes the need for any external pop-up blocker).
Other pop-ups are actually stored on your PC by malware, so that they can appear irrespective of the site you're visiting. Pop-up blockers won't stop those appearing because they only protect the path between the internet and your PC. To get rid of them you need to do a thorough scan with a decent malware removal program.
Unlike anti-virus programs and firewalls (which run 'in the background') you can have as many anti-malware programs on your PC as you like. (They only run 'on demand', so conflicts can't occur). Most people find that using the free versions of Ad-Aware and/or Spybot Search & Destroy will do the job.
http://download.cnet....-8022_4-10045910.html
http://www.safer-netw...n/spybotsd/index.html
Chris