If your using IE6 then the pop-up stopper in that is not bad, most likely you've got an adware/spyware infection. Get your self some tools to clean your machine first, Spybot S & D, Adaware are the tools most peeps use and they're free. You should also be using a firewall, Zone Alarm is good & again free.
Once you've done that, configure your browser to block &/or ask about pop-ups..
PS: As I've just remembered have a read
HERE
Have fun