Archived from groups: microsoft.public.windowsxp.general (
More info?)
"Gordon" <gordon@gbpcomputing.co.uk.invalid> wrote in message
news:OG1OUEStFHA.2756@TK2MSFTNGP09.phx.gbl...
> "Jatinder" <Jatinder@discussions.microsoft.com> wrote in message
> news:B01A9E7C-124E-4C68-827D-C0F2B16DE597@microsoft.com
> > My question is i had installed Xp Pro on my system then later i
> > installed windows 2003, before my Master Boot Record was Xp, so now
> > will windows 2003 bcome my MBR or still Xp is my MBR. Some ppl say
> > 2003 is higher version so it will take over MBR.
> > So which partion is now MBR XP or Win 2003?
>
> I don't quite understand what you mean. The MBR is a file on a sector on
the
> HDD that holds information on what Operating system(s) you have installed.
> There isn't an "XP" MBR or a "2003" MBR. If you have installed Server 2003
> over the top XP the MBR will only contain the 2003 record. If you
installed
> 2003 on a separate partition, then the MBR should contain two records - XP
> and 2003.
>
>
The master boot record contains the following structures:
Master Partition Table: This small table contains the descriptions of the
partitions that are contained on the hard disk. There is only room in the
master partition table for the information describing four partitions.
Therefore, a hard disk can have only four true partitions, also called
primary partitions. Any additional partitions are logical partitions that
are linked to one of the primary partitions. One of the partitions is
marked as active, indicating that it is the one that the computer should use
for booting up.
Master Boot Code: The master boot record contains the small initial boot
program that the BIOS loads and executes to start the boot process. This
program eventually transfers control to the boot program stored on whichever
partition is used for booting the PC.
Operating system specific boot records are located on the volume boot
sector. This is not to be confused with MBR.
Each volume boot sector contains the following:
Disk Parameter Block: Also sometimes called the media parameter block, this
is a data table that contains specific information about the volume, such as
its specifications (size, number of sectors it contains, etc.), label name,
and number of sectors per cluster used on the partition.
Volume Boot Code: This is code that is specific to the operating system that
is using this volume and is used to start the load of the operating system.
This code is called by the master boot code that is stored in the master
boot record, but only for the primary partition that is set as active. For
other partitions, this code sits unused.
In conclusion, the MBR matters not as long as its calling the active
partition for booting. When an operating system is installed, a new MBR is
installed. The operating system boot code is not located in the MBR,
rather, the partition its called for booting. Windows installs, no matter
the version, always overwrite the previous MBR. However, the new MBR has no
bearing if it calls the same partition for booting. A blank hard drive has
no MBR, so the windows install always overwrites a previous one if it
exists. The simplist way, whether a previous MBR exists or not, is to
overwrite it rather than to present an option not to.
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