If your hard drive dies carrying important files that can't be resurrected with the aid of programs like Norton or TechTool, that's a painful way to learn that you must do regular system maintenance like defragging your hard drive and backing up your files to keep them safe. But these days, keeping backups of files is only part of what you need to do to keep your work safe.
It'd be simpler if computers simply worked and didn't crash, wouldn't it? But crash they do, and some of the worst crashes I've seen in my job as a tech support agent have happened because of spyware and virus infections. The Internet has become a truly treacherous place for Windows users (Mac and Linux users are largely immune to such problems at this point) and malware infections can be difficult to remove; the best thing to do is to protect yourself.
The first thing you need to do is to make sure you have a firewall installed and have a decent antivirus program like McAfee VirusScan (my personal favorite) or Norton Antivirus, and have the program set to regularly update your virus profiles. The best antivirus program in the world won't do you any good if you're exposed to a brand-new virus that the program can't recognize because it hasn't been updated (and on that note, make sure that you check for and install system and security updates for your computer's operating system on a regular basis).
The best thing to do is to try to avoid exposing yourself to viruses in the first place. Many people get infections through spam emails that contain viruses masquerading as other types of attachments. So, don't open those attachments promising pictures of Britney Spears cavorting naked with the Queen of England, folks. Don't even touch them.
Also, don't respond to alarming emails that purport to come from your bank or credit card company. Don't click on the links they provide, don't call the phone numbers they provide, and in the name of all that is holy, don't click or call and then provide any personal information or account numbers. These emails are almost always scams intended to steal your information so that some creep can clean out your bank account or go on a credit spree on your dime. These assholes are ruthlessly efficient, and they will start doing this within minutes of getting your information. If you're worried about your account, look up the company's name in your telephone book and call them.
And finally, never, ever email anyone your entire social security number, credit card number, password, etc.
An email is about as private as a postcard, or a conversation on a crowded bus. You would be amazed at the sheer number of people who potentially have access to your emails as they make their way from Computer A to Computer B. This a good reason to never put your social security number on a manuscript that you send through email or in an emailed contract.