The best way to stop such things is to never allow them to install themselves in your system in the first place. If you're getting popups before you can even open your mail, it sounds like you may have a piece of spyware on your system. Some of these things pop up ads on your desktop without your intervention, track personal information without your consent and are a security hazard to boot.
I strongly recommend using a program called SpyBot Search and Destroy, a very comprehensive, powerful and free spyware-elimination tool. The program can also take proactive measures to keep your system from being invaded in the future, which is an excellent feature. You can get the program here (http://beam.to/spybotsd/)-- you may be astonished at how much it turns up. Another program I recommend is LavaSoft's AdAware (www.lavasoft.de). I have found that each program traps things the other doesn't, and can also perform proactive lockdowns (i.e., securing the system against spyware) that the other doesn't.
Another approach is to replace Internet Explorer with another browser which is less vulnerable to the ways spyware attempts to install itself in your system. Many users, myself included, recommend Firefox (www.mozilla.org) as an excellent substitute. If IE is required, patching with Windows XP Service Pack 2 (on Windows XP systems) should be mandatory, since XP SP2 does toughen IE considerably against unauthorized components.
This was first published in July 2003