These files are created by chkdsk and contain unsalvageable file-fragments. Usually the files in these folders are the lost temporary files, which were created but could not be correctly released or closed. They can be deleted with no harm, except if they contain documents that you would like to retrieve in any possible form. Such files are more likely to occur on FAT32 disks than on the more advanced NTFS file-system.
However, it is worrisome that they exist all, since normally they were files that were open and created by some program that was brutally interrupted without Windows being able to clean up after it. This can have two explanations:
- Someone turns off the external disk or even the computer brutally by cutting off the current, or
- Your Windows hangs often, maybe because of hardware problems, even in the drive itself.
In short, these files should not exist under normal conditions, and if they continue to occur you should rather treat first the root cause for this happening.
+1 They are basically retrieved files, but will mostly be non readable :) – Ganesh R. – 2009-10-11T13:32:52.793