Your PC's hard drive may have half a terabyte of data on its platters, and you might not remember the last time you backed any of it up. In all likelihood, though, you use only a few gigabytes' worth of files on a regular basis. With a combination of cloud-storage services, you can keep that data backed up and synced among all of your computers automatically, and access your most essential files whenever you want.
Cloud-storage services take three distinct approaches: backup, folder syncing, and drop boxes. We've yet to find a single service that offers the perfect blend of all three, but you can easily combine a couple of services, and many great options are free.
Backing up the entire contents of your hard drive to the cloud comes with a trade-off. What you get is peace of mind--the knowledge that your data is safe in the event that your home vanishes into a black hole that somehow leaves the rest of the planet intact.
What you give up is speed: Even with a very fast broadband connection, backing up all of your data can take weeks. Once the initial backup is done, however, regular daily backups of just the newly changed files take almost no time at all, and happen in the background with no effort on your part.
Restoring data can be painless and quick if you just want to recover a recent version of a particular file, but if you ever need to run a total system recovery, it could take days. Fortunately, most cloud-backup services offer the option of mailing you a recovery disc with your backed-up data on it.
My favorite choice for whole-drive backup, mostly for its great pricing, is a service called BackBlaze, which charges $5 monthly or $50 annually for backing up unlimited data on one computer. Competing backup services run as much as $90 a year for a mere 100GB.
If you move between two or three computers on a regular basis, having user folders such as Music or Documents synced between them automatically can be helpful. Sync services such as SugarSync and Microsoft Windows Live SkyDrive can sync any folders you designate, no matter where they are on your system.
SugarSync gives you up to 5GB of synced storage for free, which ought to be plenty for a typical Documents folder containing nothing but Word docs and spreadsheets. If you want to include all your photos and videos, however, you'll likely need a lot more capacity. SugarSync obliges with options ranging from $50 a year for 30GB to $400 annually for 500GB. The service includes support for Windows, Mac, iOS, Android, BlackBerry, and Windows Mobile, so you can access your files from just about any device you own.
Windows Live SkyDrive offers 25GB of synced storage for free, but supports a narrower range of devices. At press time only Windows PCs support SkyDrive folder syncing, though Macs can access shared data by going to the SkyDrive Website. Smartphones, on the other hand, can share only photos (via a mobile browser) with SkyDrive, and have no access to other file types stored there. What SkyDrive does well, however, is share files between your desktop Office programs and Microsoft Office Web Apps.
For quick syncing of critical files between multiple systems, it's hard to beat a drop box, which is a simple folder that connects to a cloud service for automatic synchronization. Just put any file in your drop-box folder, or create any subfolder in it, and that item will instantly appear in the corresponding drop-box folder on any computer or mobile device using the same account.
Drop-box services differ from folder-syncing services in that they sync subfolders and files only within a single drop-box folder; they don't allow you to designate any other folders on your drive for syncing.
The best drop-box software around is the aptly named Dropbox, which comes with 2GB of free storage that you can upgrade to as much as 8GB by spamming your friends to try it out. (Good luck, though; most of your friends are probably already using it.) Amazon recently launched Cloud Drive, which looks like a serious contender with 5GB of free storage.