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A corrupted Outlook database trashes your e-mail archive and contact list. An accidentally deleted folder wipes out critical business documents. A sudden hard-drive failure destroys your MP3s and photo libraries. The list of potential catastrophes goes on and on, and few users are prepared to deal with them. That's because they lack a diversified backup plan.

From a certain point of view, data is a little like money. Financial advisors always recommend maintaining a diversified portfolio, the idea being that if one stock or mutual fund tanks, you won't go broke. The same concept applies to backups: By diversifying your approach--that is, archiving your data in multiple places using multiple methods--you're safe even if disaster strikes one location or collection of data.

Let's take a look at the ways you can expand your backup portfolio to protect against the inevitable data catastrophe. To ensure the safey of your important files, I recommend using at least a few of the following methods in unison.

Method 1: The Full-System Backup

With external 300GB hard drives readily available for as little as $100, there's no reason not to keep one plugged into your PC. Pair it with a drive-cloning utility like Casper 4.0, which can perform scheduled, incremental backups with or without compression. A full-system backup to an attached drive is your best line of defense against data loss: In the event of total failure, it's a simple matter to restore every bit and byte to a replacement drive.

Method 2: The Remote, Data-Only Backup

While it's great to archive your entire hard drive, don't overlook the benefits of backing up just your critical data: documents, bookmarks, financial records, e-mail, address books, and so on. Why bother? Simple: Sometimes you just want to restore a handful of files or a select chunk of data. Plus, data-only backups take a lot less time than full system backups.

For this step, look to an online backup service like iDrive or MozyHome. Both offer 2GB of free storage and the option to upgrade to unlimited storage for $5 a month. Mozy relies on client software to help you select both common file types to back up and important user data files for programs like Outlook and Quicken, while iDrive uses an Explorer-style interface for selecting specific files and folders to preserve. The real advantage to both services is that they work automatically and in the background, uploading new and changed files while you work (or at scheduled times). That kind of set-it-and-forget-it backup is well worth a few bucks every month.

If you'd rather save your pennies and don't mind taking a more hands-on approach, loads of services let you park files online free of charge. ADrive, for one, offers 50GB of absolutely free storage. However, no synchronization is involved: It's up to you to pick and choose which files to upload, and when. Thus, use these services for files that don't change all that often, like MP3 and photo libraries.