On Wed, 14 Mar 2007 14:59:07 +0100, "Mark"
<markantispam@orange.fr> wrote:

>
>"Rod Speed" <rod.speed.aaa@gmail.com> wrote in message
>news:55p1ukF25k2eaU1@mid.individual.net...
>> Mark <markantispam@orange.fr> wrote:

>> Nope, not if you format the partition other
>> than the once that has ntldr and boot.ini in it.
>
>OK, but is the ntldr and boot ini not always on the same drive as windows?

Not necessarily, but there is a handoff from bios to OS
control, in that whatever drive was booting to the point
where NTLDR was found, Windows also needs to know the
controller and drive partition it will use to proceed. It
needs this because that's how they designed it, it could
have kept using the same volume unless told not to but it's
not designed to do that because of some exceptions like
persistent drive IDs and multibooting scenarios.




>>
>>> Why would you want to keep an MBR?
>>
>> When XP is being installed along with another OS etc.
>>
>>> But clearly the answer is no the basic win xp installer does not
>>> remove an existing MBR, only creates one if none is present?
>>
>> Correct.

When XP is installed with another OS already present, yes it
does write it's own MBR, it does not only do this if there
was no other MBR present. After writing it's own that
points to the active paritition, there lies the NTLDR and
boot.ini file to specify the other / prior MBRs.

However, if you had a drive overlay or other memory resident
MBR, properly running because it was loaded from the boot
device, when something else tries to write to the MBR, that
active MBR code will redirect to another location so it
retains control, and that other location is similarly,
continually treated as the alternate MBR location so long as
the boot device is still the one with that MBR capability.


>>> Apparently there is a tool to fix an MBR: 'fixmbr'
>>
>> Correct.
>>
>> Its safer to wipe the drive with somethig like clearhdd tho,
>> that eliminates a variety of other possibilitys too, particularly
>> a bios overlay that can survive even an fdisk /mbr etc.
>
>What is a BIOS overlay?


For the purpose of the discussion, any overlay that does as
mentioned above, which redirects attemps to write an MBR to
an alternate MBR location such that when the device boots it
then loads it's code before redirecting to that location to
boot.

We don't need to consider all of this though, all you need
to do to get rid of the phantom OS entry is to edit your
boot.ini file and delete the appropriate lines which will be
obvious when you look at it.