John, If you have windows XP you are probably getting the popups from the Messenger part which was activated long after XP was launched. Very few popup killers will stop them. You need to disable Messenger within XP to stop them. Instructions below.
There is the cure for Messenger popups within XP. Open the Control Panel from the Start menu. In Category mode click on Performance then Maintenance. Click on Administrative Tools then double click Services. Scroll down the right hand list & double click the Messenger entry. Click the Stop button & select Disable from the Startup menu. Click OK to apply. You should no longer be bothered with these popups
Installing Mozilla is another option. No more pop-ups, and you get tabbed browsing, my latest "can't live without" feature. You can bookmark a set of tabs, so for example, clicking one bookmark opens up several woodworking forum sites at the same time. Coool... 8)