You don't need to be paranoid about computer viruses--just alert, aware, and willing to take steps to protect yourself.
Install an antivirus utility and update it often. An antivirus program is simply the most essential software you can add to your PC. For reviews of products, see "The SWAT Team." Consider your options during setup; at a minimum, you should enable full-time automatic scanning and make sure the utility checks the contents of .zip and other compressed files.
Antivirus vendors update their virus definitions--the files they use to spot viruses--every week. For maximum safety, you should update that often, too. Some utilities can automatically add definitions as they become available.
Be cautious about macros. Safeguard your PC by enabling macro security options in your software packages. In such Office 2000 apps as Word and Outlook, for example, select Tools, Macro, Security... and be certain that the Security Level is set to High or Medium.
Update your Internet software. The majority of today's viruses arrive via e-mail, so make sure your e-mail program is up-to-date. Microsoft Outlook is the focus of most e-mail-based viruses, and Microsoft regularly releases new security patches. Don't ignore your Web browser either. The latest patches close some ActiveX and Java security holes.
Keep your brain in gear. Don't open attachments from people you don't know, and be suspicious of attachments from those you do. Be especially wary of any file that has a .vbs extension. Even if you think it's a legitimate file, don't open it with your e-mail program. Save it to disk and run it through a virus scanner first.
Protect your network. If you're responsible for networked PCs, you may want to block users from receiving particular types of e-mail attachments, such as .exe or .vbs files. Server-based e-mail programs offer sophisticated versions of this functionality, but Outlook carries only a bare-bones version. Don't ignore the balance between security and productivity: Blocking all .doc files might help keep macro viruses away, but it will also hamper your ability to work efficiently.
Back up frequently. Whether you run a home PC or a corporate network, regular backups are essential in case your precautions fail and a virus does sneak in.