No matter how good your pop-up blocker is, every so often one of these suckers slips through. No big deal, right? You just click on the 'X' to close it, right? WRONG!

Here's a quick tip for how to close pop-ups safely.

You don't want to click on that 'X' because some nasty pop-ups may deliver malicious software to your computer no matter where you click, even clicking the 'X' to close the pop-up window.

We know this because of the horror stories sent by users to Jessica Dolcourt at CNET Download.com.

Here's what to do to avoid the malicious software.

Step One: Read the Cover of the Hitchhiker's Guide to the Galaxy. (I other words, Don't Panic!)

Step Two: Press CTRL-SHIFT-ESC to call up the Windows Task Manager.

Step Three: In the Applications tab, and look for the title of the pop-up. If you're not sure, click the pop-up in the taskbar, don't click the actual pop-up Window and then examine the title bar. You may need to close a few applications to narrow it down. Just remember not to click the pop-up!

Step four: Once you've identified the offending pop-up, select it in the Task Manager, and press End Task.

Hope that keeps you free of malicious software. Of course, you should always run antivirus and antispyware. Head to CNET Download.com to find and download our favorites.