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Norton Utilities 5.01 Error Messages (Users)

posted by Arjay, 13.08.2012, 12:00

> > Otherwise, I don't see the urgency as all of that data is deleted
> anyways,
> > hence presumably not very important. (But I could be wrong ....)
>
> In MS-DOS at least, when a file is deleted it is only removed from the
> FAT, not actually removed from the disc until it is over-written.
Correct, the first character of the filename in the FAT is replaced with 0xE5 to basically say the space occupied by this file is now available for re-use. From something I was reading the other night I now understand that the choice of using 0xE5 goes back to CP/M in that CP/M disks were formatted with 0xE5 hence Marc McDonald choose to use 0xE5 as the marker for deleted files in FAT for M-DOS since in the CP/M world it is saying "this part of the disk has already been formatted" without requiring all of the sector to be re-formatted.

Providing new data has not already started to be written onto the disk then most decent data carving tools such as Foremost, Photorec, PhotoRescue should work well for recovering most data. However no tool is full proof particularly as problems of data recovery occur with the fragmentation of files.

Therefore if it is not easy to plug the drive into another machine (which incidently has risks) - what I would do is dump the entire harddisk to a file or series of files which I then rejoin/can reimage to another drive etc. In NU this can be done using the save sector option, e.g. multiple sectors can be saved over a series of floppies. This then allows the data to be easily viewed/processed with recovery tools.

This should be possible even on very old machines and also under Linux/Windows using similar tools (e.g. ports of Unix's DD).

Years ago I did just this on an 8086, saving out an old 30Mb hard drive sector by sector to floppies. Yes, extremely painful and slow but it enabled me to run various tools and importantly manually process the data as a single file allowing more data to be recovered than would possible otherwise.

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