DiskPatch manual - Tutorials - FAT boot sector repair

Recovery Guides: step-by-step DiskPatch operations:
FAT Boot Sector repair.

A list of terms used in this page and their explanation can be found here.

This guide describes a DiskPatch function in condensed form: if you need additional information, read the corresponding part of the manual.

Problem :	boot sector damaged/deleted, no partition access
Symptoms :	partition appears as unformatted, "partition needs to be formatted", "unknown file system", file system identified as RAW
Solution :	rebuild the boot sector

Things you need to know before we start:

In the world of disks and data recovery we start counting disks at 0 (zero). So the first disk is 'disk 0', the second disk is 'disk 1', etc.
Use the cursor keys to navigate the menus, use the <Enter> key to select an option, use the <Escape> key to abort or leave a menu.
Pressing <Escape> at any time during the repair will abort the repair and leave the disk unchanged, with the exception of the FAT synchronize function: if this has been initiated, aborting it WILL leave the disk in an altered state. Use the undo to revert changes.
By performing this operation until this step, you can check the validity of the boot sector.
If you're using the trial version you can run this repair to completion; nothing is saved to disk when using the trial version. Use this to get an idea about whether the boot sector can be rebuilt.

Here we go:

Start DiskPatch and select the problem disk.

(example: your screen will differ)

After selecting the disk, the menu will expand, showing actions that can be performed for the selected disk.
The selected disk will be marked in high intensity blue in the disk list (disk 0 in our example).

Now select 'Perform repairs', then 'Rebuild boot sectors'.
DiskPatch will ask you if you wish to create an undo file (recommended), if this option is enabled.
Enter a description or leave the default suggested text. Press <Escape> at this point to skip creating the undo file (not recommended).

A list of partitions is displayed. Select the appropriate partition and press <Enter>.

The following menu is displayed:

Select 'Check and Fix Boot sector'. The other options are not relevant at this time and will be explained in other parts of the guides.
DiskPatch will now analyze the partition.

The 'Repair partition' display shows the progress for the current analysis/repair.
A number of things are checked during the 'boot sector repair' operation. If the result is okay, 'done' will be displayed in green. If problems are found for that particular test, 'done' will be displayed in red. If a result could not be determined (because not enough data was found to make a reliable estimate) the result of the test will be displayed in yellow.
When the analysis is complete the following menu is displayed:

Please note: depending on the type of problem this display will show different results. In our example some values in the boot sector are incorrect, which results in the screen as displayed above. If the boot sector was deleted entirely (and filled with blanks) the screen would look something like this:

Because no values are found if the boot sector is completely wiped, some tests can not be run and will display a result in yellow. These tests will be performed as soon as the values that are needed have been determined (during the actual repair phase); this should have no adverse effect on the repair.

This menu allows you to enable or disable repairs. If repairs are needed, DiskPatch will have set the appropriate repair option to 'yes'. If no repairs are needed, all repair options are set to 'no'.
As you can see, in our example there's something wrong with this boot sector. Select 'View analysis details' if you wish to see more:

Severe problems (that require repair) are displayed in red. Problems displayed in yellow will not affect the partition negatively but will be repaired if a repair is started.
In our example 'sectors per cluster' is incorrect, as is the total number of sectors for this partition. These values must be corrected before the partition can be accessed again. Press any key to exit the 'details' display.

Now select 'Continue' to start the repair. DiskPatch will perform the steps needed to recreate the boot sector.

If you're using the trial version DiskPatch will not save any changes to disk, so it's safe to let this repair run to completion. This is actually a 'feature' of the trial version; this way you'll get an idea if things can be fixed.

Some of these steps may take some time, in which case a progress bar is displayed:

If all necessary data is found and the repair can continue, the following display will appear:

Note: selecting a directory as root cluster is only needed when a FAT32 boot sector is being repaired; this display will not appear if you're repairing a FAT16 or a NTFS boot sector.

To rebuild a FAT32 boot sector, DiskPatch needs to locate the root directory for that partition. If DiskPatch finds a candidate it will display this sector as if it was a root directory. This will allow you to determine whether DiskPatch picked the right sector or not. In our example you can clearly see that this sector is the right one; the file and directory names are the ones that were in the root directory before the partition problems occurred.
If a sector is displayed that is obviously not the right sector, select 'Continue scanning'. If the currently displayed sector is the root directory, select 'Select as root cluster'.
The repair will now continue. If the repair is completed successfully the following completion screen will appear:

If the 'Boot sector status' and 'FAT status' are both 'Ok', the repair has been completed successfully.
Press a key to leave this display, you will be returned to the 'select partition for repair' display.

The label for the partition is changed to 'REPOMAN' to indicate that DiskPatch has rebuilt the boot sector for that partition. You can change that later, when you have access to the partition again.

This completes the repair.