Hi there Srinivas,
Essentially, one fixes the boot sector helps the NT Startup process (NTLDR)
to find the MFT (Master File Table) and execute the rest of the bootstrap
process.
From time to time, usually due to hardware failure or virus infection, a
boot sector may become corrupted. If the partition is the active primary
partition, or a partition containing operating system files, this can
prevent the system from starting. Otherwise, it may simply prevent access to
data on the drive.
The Master Boot Record, created when you create the first partition on the
hard disk, is probably the most important data structure on the disk. It is
the first sector on every disk. The location is always track (cylinder) 0,
side (head) 0, and sector 1.
The Master Boot Record contains the Partition Table for the disk and a small
amount of executable code. On x86-based computers, the executable code
examines the Partition Table, and identifies the system partition. The
Master Boot Record then finds the system partition's starting location on
the disk, and loads an copy of its Partition Boot Sector into memory. The
Master Boot Record then transfers execution to executable code in the
Partition Boot Sector.
So now that you know which does what, you should have a good idea as to what
to use where. In situations where there is no apparent disk corruption and
the OS is unable to start, then Fixboot is the one to choose. In cases of
disk level/partition level corruption, then Fixmbr enables repair of the
MBR.
For more info on disk internals, take a look at
http://www.microsoft.com/windows2000/techinfo/reskit/samplechapters/fncb/fncb_dis_zdnc.asp
FIXBOOT
Use this command (where drive name is the drive letter where the boot sector
will be written) to write the new Windows boot sector code on the boot
partition. This command fixes problems where the Windows boot sector is
corrupted. The Emergency Repair process also fixes the boot sector. This
command overrides the default of writing to the system boot partition.
FIXMBR
Use this command (where device name is an optional device name that
specifies the device that needs a new MBR) to repair the master boot record
(MBR) of the system partition. This command is used in scenarios where a
virus has damaged the MBR and Windows cannot start.
WARNING: This command has the potential to damage your partition tables if a
virus is present or a hardware problem exists. This command may lead to
inaccessible partitions. Microsoft suggests running antivirus software
before using this command.
The name can be obtained from the output of the map command. If this is left
blank, the boot device's MBR is fixed, for example:
fixmbr \device\harddisk2
If Fixmbr detects an invalid or non-standard partition table signature, it
prompts you for permission before rewriting the MBR.
--
Regards,
Jeff Low
Microsoft
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