Repair Windows XP by using the XP installation CD

"John John (MVP)" wrote in message ...
Franc Zabkar wrote:
On Mon, 01 Sep 2008 09:33:24 -0300, "John John (MVP)"
put finger to keyboard and composed:


Franc Zabkar wrote:


BTW, if I can get my hands on an XP CD, I'll try a few experiments to
see if I can reproduce the FAT12 problem.

You can download the 6 floppy diskette setup set from Microsoft or download an .iso copy of the Recovery Console on several web
sites.

John


I tried a few experiments on a 13GB FAT32 volume that had been
formatted by Win98SE.

It should first be noted that the boot sector consists of a data
section at the beginning and a code section at the end. After running
FIXBOOT, the data section remained intact but the code section was
replaced with XP boot code. This is expected behaviour, so you were
right. I apologise.

I then tried damaging the data section by replacing the FAT32
signature with "JUNK ", but FIXBOOT once again correctly detected the
sector as FAT32 and replaced the boot code. However, it did not
restore the FAT32 signature.

Next I completely zeroed the boot sector. This time FIXBOOT created a
10MB FAT12 volume. At no time did it use the backup boot sector at
sector 6. In fact, I have demonstrated in the past that the XP
installation process does not update the backup boot sector, instead
it leaves the original Win98 version intact. It appears that XP is not
even aware that it exists.

Yes, if I remember correctly I believe that fixboot does not use the backup boot sector if it was created by Windows 98, in other
words the backup boot sector would have to be NT (XP) compatible for fixboot to use it as a backup. Remember that fixboot is a
Windows 2000/XP utility, it doesn't care about W9x problems and it won't attempt to restore a W9x boot sector, it will attempt to
restore an NT compatible boot sector. I think that if the drive had been formated with Windows 2000/XP that fixboot would have
used the backup boot sector.


All other things being equal, the only difference (between a FAT volume formatted
by 9x or NT) should be the loader code portion of the boot sector. The BPB
data and the backup boot sector location should be the same.

It may be significant to note that the backup boot sector "pointer" is located
in the BPB, and Franc zeroed that out, so...



So as you can see, FIXBOOT works fine repairing boot sectors that
aren't really broken, but it can create a disaster when there is a
genuine problem, even an easily fixed one.

Create a disaster? Hardly, the disaster was created when you went to the extreme of zeroing out the boot sector! Being that
there was no compatible sector to use as a replacement fixboot barfed and wrote a FAT12 boot sector to the drive, the end result
was no worse than having a zeroed out boot sector, the boot sector was already trashed before fixboot ran! Fixboot does not trash
or change FAT32 partitions into different partitions, when these problems occur the boot sector was already completely thrashed so
you cannot put the blame on fixboot, the only thing that you can put on fixboot is that it could not overcome the problems caused
by an already completely borked boot sector, fixboot left the old backup boot sector in place for you to manually recover, fixboot
created no more of a disaster than what was already present. Fixboot is not an advanced data recovery tool and it cannot overcome
all boot sector corruption problems, in cases when fixboot cannot recover the boot sector Microsoft advises users to manually
recover the boot sector.

John

On Tue, 02 Sep 2008 09:39:37 -0300, "John John (MVP)"
put finger to keyboard and composed:

Franc Zabkar wrote:

I tried a few experiments on a 13GB FAT32 volume that had been
formatted by Win98SE.

snip

Next I completely zeroed the boot sector. This time FIXBOOT created a
10MB FAT12 volume. At no time did it use the backup boot sector at
sector 6. In fact, I have demonstrated in the past that the XP
installation process does not update the backup boot sector, instead
it leaves the original Win98 version intact. It appears that XP is not
even aware that it exists.

Yes, if I remember correctly I believe that fixboot does not use the
backup boot sector if it was created by Windows 98, in other words the
backup boot sector would have to be NT (XP) compatible for fixboot to
use it as a backup. Remember that fixboot is a Windows 2000/XP utility,
it doesn't care about W9x problems and it won't attempt to restore a W9x
boot sector, it will attempt to restore an NT compatible boot sector. I
think that if the drive had been formated with Windows 2000/XP that
fixboot would have used the backup boot sector.

You missed the point. Windows XP was installed onto a clean FAT32
partition created by Win98. This *installation* process had no reason
to retain a Win98 backup boot sector, yet it did not replace the
backup with one of its own. This suggests that XP does not use a
backup boot sector under any circumstances. At the very least, the
installation procedure is flawed.

Had XP bothered to consult the backup boot sector, then it could have
made use of its data section and added its own boot code, as I had to
do manually afterwards. In retrospect, I could have just copied the
Win98 backup from sector 6 to sector 0, and then run FIXBOOT to
convert the code section. But by then I was too shell-shocked to trust
FIXBOOT to do anything correctly.

So as you can see, FIXBOOT works fine repairing boot sectors that
aren't really broken, but it can create a disaster when there is a
genuine problem, even an easily fixed one.

Create a disaster? Hardly, the disaster was created when you went to
the extreme of zeroing out the boot sector! Being that there was no
compatible sector to use as a replacement fixboot barfed and wrote a
FAT12 boot sector to the drive, the end result was no worse than having
a zeroed out boot sector, the boot sector was already trashed before
fixboot ran!

The stupid thing was that XP wrote anything at all, let alone a floppy
drive volume. If anything, it should have been smart enough to consult
the partition table and recreate a default boot sector based on what
it found there, in the exact same way that it would have done during a
format.

BTW, Windows 98SE has absolutely no problem with a zeroed boot sector
because it is smart enough to see the backup, even in the absence of
the pointer that Bill mentioned.

Fixboot does not trash or change FAT32 partitions into
different partitions, when these problems occur the boot sector was
already completely thrashed so you cannot put the blame on fixboot, the
only thing that you can put on fixboot is that it could not overcome the
problems caused by an already completely borked boot sector, fixboot
left the old backup boot sector in place for you to manually recover,

Hmm, so if FIXBOOT knew about the backup boot sector (which I don't
believe is true), then why wasn't it smart enough to use it?

fixboot created no more of a disaster than what was already present.

AFAICS the disaster would be compounded when you write to the FAT12
volume. I believe you will trash the first copy of the original FAT
because the new root directory will now be located within its space.
That appears to be what happened in my case, when XP wrote its system
information stuff to the drive. This still presents no problem for
Windows 98's Scandisk which can repair such errors (by using FAT#2 to
reconstruct FAT#1), but XP's CHKDSK wasn't able to do this.

Fixboot is not an advanced data recovery tool and it cannot overcome all
boot sector corruption problems, in cases when fixboot cannot recover
the boot sector Microsoft advises users to manually recover the boot sector.

John

The problem is that Fixboot didn't fix anything at all. Instead it
made the problem worse. I would think that a better strategy would be,
if you don't know what's wrong, then don't fix it, or at least make an
intelligent attempt. Writing a 10MB floppy boot sector to a 38GB hard
drive partition is indefensible.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On Wed, 03 Sep 2008 06:47:30 +1000, Franc Zabkar
put finger to keyboard and composed:

On Tue, 02 Sep 2008 09:39:37 -0300, "John John (MVP)"
put finger to keyboard and composed:

Create a disaster? Hardly, the disaster was created when you went to
the extreme of zeroing out the boot sector! Being that there was no
compatible sector to use as a replacement fixboot barfed and wrote a
FAT12 boot sector to the drive, the end result was no worse than having
a zeroed out boot sector, the boot sector was already trashed before
fixboot ran!

The stupid thing was that XP wrote anything at all, let alone a floppy
drive volume. If anything, it should have been smart enough to consult
the partition table and recreate a default boot sector based on what
it found there, in the exact same way that it would have done during a
format.

BTW, Windows 98SE has absolutely no problem with a zeroed boot sector
because it is smart enough to see the backup, even in the absence of
the pointer that Bill mentioned.

Even Win98 in real DOS mode can see the entire file system from a DIR
command. By applying a SYS command to this damaged volume you can
reconstruct the primary boot sector from the backup.

However, zeroing both the primary and the backup boot sectors results
in "invalid media type" and "general failure" errors. No disc tool
(Sys, Debug, Scandisk, Chkdsk) is then able to access the drive. So it
appears that SYS.COM cannot reconstruct the boot sectors by referring
to the partition table, probably because the BPB can contain variable
data such as the number of sectors per cluster. However, at least SYS
knows not to write nonsense to those areas.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

On Wed, 03 Sep 2008 06:47:30 +1000, Franc Zabkar
put finger to keyboard and composed:


On Tue, 02 Sep 2008 09:39:37 -0300, "John John (MVP)"
put finger to keyboard and composed:


Create a disaster? Hardly, the disaster was created when you went to
the extreme of zeroing out the boot sector! Being that there was no
compatible sector to use as a replacement fixboot barfed and wrote a
FAT12 boot sector to the drive, the end result was no worse than having
a zeroed out boot sector, the boot sector was already trashed before
fixboot ran!

The stupid thing was that XP wrote anything at all, let alone a floppy
drive volume. If anything, it should have been smart enough to consult
the partition table and recreate a default boot sector based on what
it found there, in the exact same way that it would have done during a
format.

BTW, Windows 98SE has absolutely no problem with a zeroed boot sector
because it is smart enough to see the backup, even in the absence of
the pointer that Bill mentioned.


Even Win98 in real DOS mode can see the entire file system from a DIR
command. By applying a SYS command to this damaged volume you can
reconstruct the primary boot sector from the backup.

However, zeroing both the primary and the backup boot sectors results
in "invalid media type" and "general failure" errors. No disc tool
(Sys, Debug, Scandisk, Chkdsk) is then able to access the drive. So it
appears that SYS.COM cannot reconstruct the boot sectors by referring
to the partition table, probably because the BPB can contain variable
data such as the number of sectors per cluster. However, at least SYS
knows not to write nonsense to those areas.

My initial point was that fixboot does not trash FAT32 partitions and it
does not change them to FAT12 unless the boot sector is totally borked
to begin with, your trials support my point. As for the contentious
issue of fixboot writing a FAT12 sector on a totally borked one as far
as I am concerned that is a non-issue, whether or not a FAT12 sector is
written the boot sector still needs to be recovered from the backup, it
changes absolutely nothing. Also, fixboot does not rewrite the backup
boot sector, that is still available for manual recovery.

Incidentally (on FAT32 drives) in certain instances when fixboot cannot
restore the boot sector Microsoft does tell users to resort to the
Sys.com utility to restore the W9x boot sector and to then issue the
fixboot command again to write the necessary NT code.

John

well when i reinstalled it again theres an error saying Dll.exe was not found huhuh