How to protect your computer

If you think you've got malware, follow these steps:

1. Disconnect your computer from the Internet and its power source, then reconnect the wires and restart in safe mode. On a Windows PC, hold down F8 as soon as the reboot begins, then choose "safe mode" from the menu that appears. On a Mac, hold down the shift key while restarting.

Check for updates to your antivirus software, then perform a complete scan.

2. If your antivirus software is acting strangely or is missing, start your computer with a rescue CD — a special disc that contains your computer's operating system and allows you to start your machine even if your hard disk is corrupted.

Sometimes a rescue disk is supplied with your computer. Or use someone else's computer to create one from free downloads at any of these sites: AVG, Avira, BitDefender or F-Secure. (You should do this before you have problems.)

3. Check the website of your antivirus software vendor for additional information or software patches that will remove a particular malicious program.

If no malware is found, but problems continue, it's best to have your computer examined by a technician.

You may also like: How to maintain your computer.

Sid Kirchheimer is the author of Scam-Proof Your Life, published by AARP Books/Sterling.