Pop-up ads are those irritating ads and messages that pop up on your screen whenever you're online. There are three major causes of pop-up ads:
Dealing with the first two types of ads is relatively easy. You can use a simple pop-up blocker like the Google toolbar to block those ads.
The Google toolbar is a nice freebie that makes it easy to search the Web. As an added bonus, it can automatically block most pop-up ads that come through your Web browser. To install the Google toolbar:
Once the toolbar is downloaded and installed, you should see it in your Web browser's toolbar area, as in the example shown in Figure 1.

Figure 1
Here are some quick tips on using the Google toolbar:
Messenger Service ads are plain-text pop-ups, like the example in Figure 2. Like most such ads, the information in that one is lie and something you should definitely ignore. Better yet, just block these things so you don't have to put up with them at all. The steps below describe how to block those ads using Windows XP:

Figure 2
Caution: Follow the steps below very carefully. There is no margin for error in this operation. So now is not a good time to experiment or be careless.

Figure 3
That should take care of the Messenger Service pop-ups.
Any remaining pop-ups will be coming from some program on your system. Examples of programs that are notorious for producing pop-ups are the peer-to-peer file sharing programs like Kazaa, Morpheus, and AudioGalaxy. The only way to block pop-ups from such programs is to actually remove them from your computer using Add/Remove Programs in Control Panel.
If you really don't want to part with the service the program provides, see if you can find an equivalent program that doesn't do pop-ups. For example, if you're willing to part with $18.88 (or whatever the price might be) for six months worth of downloading and updates, without any pop-up ads, you can purchase and installed LimeWire Pro from LimeWire's Web site at www.LimeWire.com.
Spyware and Adware are other ways advertisers find you. Lavasoft's Ad-Aware is a great program for finding and eliminating those items from your computer. There's a version you can download and use, free-of-charge, and it won't do anything nasty like cause pop-ups. For more information, see www.lavasoft.de.
If you end up with lots of open Web pages on your desktop in Internet Explorer, and don't feel like closing them one at a time, here's an easy trick. Just right-click Internet Explorer's taskbar button (shown below) and choose Close Group.

Alan Simpson