Disk Repair and Data Recovery for a FAT32 Hard Disk
Sunday, April 12, 2009 at 8:08 am
Windows Me Annoyances Discussion Forum
Posted by Ed
(659 messages posted)
Data Recovery help in an MS-DOS Batch file (350KB):
Recovery Instructions
and Utilities
The batch file in the link contains detailed instructions on how to backup and restore
the key sectors of a FAT32 hard disk (for any size of FAT32 hard disk from 8 GB to
137 GB).
Included are detailed instructions on how to use those backups to recover from a
hard disk crash, and on how to recover from a disk crash even if you do not have
those backups (a rather more difficult problem).
A great deal of information about the disk structure of a FAT32 hard disk is provided
in the file, which attempts to provide an all-purpose DIY solution to both disk repair
and data recovery.
In terms of disk repair, it tackles both repairing the data structure of a working
disk which has suffered only data corruption (due to data being written to the system
area, overwriting the MBR, Boot Sector or FAT), and fixing broken hardware (including
repairing bad sectors).
In terms of data recovery, it explains how to safely copy files from a broken disk
to a new disk (including how to install a new working hard disk), with details of
how to clone the entire broken disk and of how to copy individual files (one-by-one
or en mass).
Instructions are also included on recovering from common file system errors, such
as the "Blue Screen Of Death". Many other error messages generated by the WinME Operating
System are also tackled.
Each section in the batch file includes recommendations on which software to use,
and details of how to use it most effectively. The software is mostly DOS programs,
to enable you to carry out the work even where Windows can't load.
Included at the end of the batch file are downloads links to enable you to obtain
on-line the software mentioned in the file.
You do not need to be an expert on MS-DOS batch files. You only need to know
a little about them: for example that if you execute (i.e. run) the file, it won't
execute any line which *begins* with "rem" or with a double colon "::" as those are
used to disable ("comment out") a line.
The file contains many different solutions; so it is probably best to make a copy
of it, and delete the sections which are not applicable to your particular problem.
I happened across this file by chance. I'm not offering any support for it here:
it seems to me to be self-explanatory, so if you read it but don't understand it
then there's nothing I can usefully add.
It gives a crash-course (no pun intended!) in how to survive a disk crash. Read it
carefully before taking any steps: then read it again! Make
sure you understand what has gone wrong with your hard disk before you attempt
any recovery action.
You will need a basic understanding of the structure of a FAT32 disk. You may have
one which has only a single partition (e.g. Drive C:), or you may have one which
has more than one partition (e.g. Drive C: and Drive D:). The batch file tries to
provide the necessary basic understanding, but you will find it helpful to also read
up on the subject through Google (e.g. search for information on both FAT32 and MBR).
A disk is divided into sectors (millions of them). Each sector is usually 512 bytes
long. Two sectors thus total 1024 bytes, or 1 KB (kilobyte). Depending on the size
of the disk, usually either 32 sectors or 64 sectors make 1 cluster. The disk stores
information (files) in a cluster: so a file might only be 200 bytes of information,
but will still be alloted 1 cluster all to itself (even though 1 cluster is typically
64 sectors, i.e. 64 multiplied by 512 bytes), so a cluster can contain a vast amount
of empty space, in addition to your file's data. A file is alloted as many clusters
as it needs: and each cluster is recorded in the File Allocation Table (FAT).
A disk may contain more than one Partition; and all Partitions begin with a Partition
Table sector (e.g. the MBR, or Master Boot Record, which is the first sector on the
disk), which is typically followed 63 sectors later by the Boot Sector, which is
typically followed 32 sectors later by the first sector of the FAT (File Allocation
Table). The FAT might be 20,000 sectors (or longer), depending on the partition's
size. A second copy (i.e. a backup copy) of the FAT typically follows immediately
after the first FAT. The Root Directory table then typically follows immediately
after the second copy of the FAT. The rest of the Partition contains your files.
This batch file provides routines for making a backup copy of all of these vital
data structures: MBR, Boot Sector, FAT, and Root Directory table. It also explains
how to reconstruct them if you don't have a backup copy of them. And it tells you
where to find the tools to use to automate as much as possible of the recovery process
if you don't have the necessary backup copies of those key sectors.
The most useful tool for gaining a practical working understanding of disk structure
is probably Norton's DiskEdit (DISKEDIT.EXE). The 2001 and 2002 versions (or later)
are needed for a FAT32 disk (because earlier versions either don't work at all for
FAT32, or only work if the disk is smaller than 8 GB). Norton DiskEdit includes tools
which will find for you the starting sector of the various data structures: such
as the Partition Table, Boot Sector, and FATs.
Ed
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