Remember to use the "Safely Unplug Hardware" option. Memory cards and sticks generally tolerate immediate removal, but do yourself a favor and remember to safely eject these devices before removing them, just to be sure. This cuts down on the possibility that data will be lost in the first place.
OS: DOS, Windows 98 and later, Mac OS X, Linux (2.4 /2.6 kernel)
In some ways, PhotoRec is the most powerful application in this review. It can recover files from almost any device -- whether or not it's mounted with a drive letter, has a partition or is even formatted. PhotoRec has editions for multiple platforms: Windows, Linux and Mac OS X. And its creator claims it can detect and recover more than 390 types of files, and not just photos, as the name might imply. However, its very Spartan interface may be off-putting to users who expect a slick graphic interface.
When you launch PhotoRec, you're given a list of all the available storage devices in the system: hard drives, attached removable drives or loaded card bays -- but not networked drives. Choose a device and a partition, set your search options (the defaults work fine for basic recovery), pick a place to save the recovered files to and the rest is pretty automatic.
A recovery pass can be halted and resumed later if need be, especially if the time estimate for recovery (which is gratifyingly accurate) runs into hours. A full scan of each of my 8GB devices only took about 10 minutes, although the "unformat" option (see below) easily doubled that.
Recovery searches can be performed on either the space marked as free or on the entire drive, regardless of what files already exist. One feature that goes hand in hand with this is the "unformat" function, which analyzes the entire drive for file system structures instead of simply looking block-by-block for valid files. This is useful if you want to recover directories instead of just files (although for the most part I was happy just to get the files back).
It's even possible to recover from a device whose partitions have been damaged or which has bad directory information. You can also add your own custom file types to the program if you're looking for files that aren't in PhotoRec's dictionary of signatures.
PhotoRec restored everything I was looking for, although file names weren't recovered and CR2 files weren't saved unless I enabled an expert option to save "broken" files (possibly because they were seen as damaged TIF files). Also, even though PhotoRec runs on Windows, don't expect a GUI: it has a command-line interface.
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