You may not always be able to protect your laptop from a thief, but you can keep the data it contains safe. Two new products--PGP Whole Disk Encryption 9.5 and DriveCrypt Plus Pack 3.5--promise to protect your data, so that even if your computer falls into the wrong hands, its contents will remain unreadable. Both applications are easy to use and offer an impressive suite of tools, but most users will appreciate the more practical features and lower price tag of PGP's product.

Both PGP and DriveCrypt offer on-the-fly full-disk encryption, which means that they scramble all the data on your hard drive the moment you save it to disk. Both use the AES-256 algorithm--a fast, well-established, and trusted mechanism for encrypting data. Both protect a computer from the minute it's powered on, and give you a "single sign-on" so you have to enter your password only once per session, when you boot the PC.

The initial setup for both applications--creating an encryption key and telling the software which partitions you want to protect--takes just a few minutes. Once that's done, you can open, change, save, and close files as you normally would, and the software does all the work. Most important, the programs do their job quietly in the background and have no noticeable impact on day-to-day system performance.

The biggest differences between the two products are price--at $119, PGP's package is a better value than the $161 DriveCrypt--and additional features. Most people will find PGP's offering the better deal on both counts. For instance, PGP lets you create any number of "virtual disks," encrypted containers that the operating system treats as if each were another drive partition; this comes in handy if you want to encrypt some files on an external drive, but not the entire drive. The program also lets you create an encrypted "PGP Zip" file that you can send to others--and your recipients don't need a copy of the program to open the files within. PGP's package also includes a secure data-shredding tool for making any deleted file unrecoverable.

Still, the ultraparanoid might find DriveCrypt's feature set more compelling. The Plus Pack lets users create multiple passwords for a system, for instance. You can assign one password that grants full access to all data on a drive, and a second password that permits access to a only portion of the drive while hiding the rest.

Why would you want to do this? Suppose that someone were forcing you at gunpoint to enter your password, or suppose that you needed to assign different levels of access to company data to yourself and to members of your staff. When you create your encryption keys--a process that takes no more than three mouse clicks--DriveCrypt lets you hide the keys inside multimedia files, such as JPEG images or digital music. Hiding data inside seemingly unrelated files, a method called steganography, lets you hide these electronic valuables in plain sight, like an electronic version of a hollowed-out book on a bookshelf.

Whether you require the cloak-and-dagger features of DriveCrypt or the features of PGP that let you safely share encrypted data with others, both products provide a level of data protection that many PC users sorely need.