The most expensive (precious) part of your computer is not a piece of hardware. It is the information kept inside the box. It is easy to replace hardware. It is difficult to replace the data.
Worse yet, somebody might make a copy of the data and carry it away. And since the theft of the information leaves the original around, you won't know that the data was taken.
You need to protect your data!
If somebody were to steal that computer, or a backup from the hard disk, all of this precious secret information is in the bad guy's hands.
Use a security package to encrypt your sensitive data!
Not all security packages are equally good. Cryptography is a complex field and some companies offer products that aren't as good as they say, or aren't as good as they think. Matt Curtin wrote a short introduction to this topic called "Snake Oil Warning Signs: Encryption Software to Avoid" (http://www.interhack.net/people/cmcurtin/snake-oil-faq.html).
You need a backup copy of the data, in case the computer dies and loses all the data. Just restore from the backup and you're back in business. Of course, if the backup was taken six months ago, the restored computer will be missing a chunk of data six months long. So it is a good idea to back up frequently.
Everybody knows that backing up your computer data is a good thing, but nobody really does it. Here's how the dialog is going to go:
support: Technical support. What can I do for you? you: My computer keeps crashing. support: Have you tried ABC? you: Yes. support: Have you tried XYZ? you: Yes. support: Do you have a recent backup of your files? you: No. support: Ha ha ha! Ho ho ho! He he he! {click}
'Nuf said?