fixmbr ...

[RJK]

Can someone point me to a page that explain exactly and thoroughly what xp
pro's "fixmbr" does, when run from the recovery console ?
Specifically, what effect, if any would it have on the file allocation
tables ? ...and would it affect / retain his dual boot configuration ?

I've been googling for the past few days to get a handle on the best
approach to fix my brothers PC when I visit him in a few days. I'll be
taking a Norton a/v boot up cd to sweep his machine when I get there but, I
suspect that his problems started a few days after he installed old non-xp
pci128v sound drivers into xp pro, on his dual boot w98se / xp pro machine,
and that his problems* are not caused by a virus.

* W98se gives a "...initialising configmg..." error and xp pro tries to
start and leaves him at a black screen.

....and what does "fixroot" do ...I think I've read that that does replace
the fats...

regards, Richard

 

[Michael D. Alligood]

http://www.microsoft.com/windowsxp/.../home/using/productdoc/en/bootcons_fixmbr.asp

--
Best of luck!

Michael D. Alligood
MCSA, MCP, CCNA, A+,
Network+, i-Net+, CIW A, CIW CI

 

[RJK]

MUCH obliged, that page led me to and fro to LOTS of useful info. that's
filled in LOTS of holes in my knowledge ....which during the past few years
seems to be leaking away faster than I can replace it

regards, Richard

 

[Alex Nichol]

Can someone point me to a page that explain exactly and thoroughly what xp
pro's "fixmbr" does, when run from the recovery console ?
Specifically, what effect, if any would it have on the file allocation
tables ? ...and would it affect / retain his dual boot configuration ?

That is outside any partition of the disk and has no effect on FATs or
other file system structures. The MBR is the very first sector of a
hard disk. At boot, the BIOS looks for a 'signature' there and if found
loads the sector and jumps into it to execute the MBR code, which is
what FixMBR rewrites, That looks for the 'partition table' at the end
of the sector, which has the pointers to up to four Primary partitions,
sees which one is flagged Active, and loads the first sector of that -
the Partition Boot sector. That, which is what fixboot fixes, is
OS-specific, and looks for the loader for the OS - ntldr in the case of
XP, to load that and hand over to it. Ntldr then uses the entry in
boot.ini to find where the Windows folder is (asking you for which
system if there are others around) and gets on to load from that.

The XP dual boot happens at that ntldr/boot.ini stage and is unaffected
by fixmbr or fixboot. Other boot managers, eg BootMagic or BootITNG, or
many installations of the Linux loaders lilo or grub, will replace the
MBR code with their own stub. That fetches the rest of their own code
and tables; in the case of BING usually from a private micro partition
made in the rest of the first cylinder of the disk, which is otherwise
usually wasted. So a FixMBR will kill such a boot manager, needing a
reinstall of that. This happens when you install windows - after that
you have to restore such a boot manager.

 

[RJK]

Much obliged, ...things are gradually dropping into place. This is a
fascinating area of theory, that I'm wading around in at the moment.
While wading around during the past few days, I suddenly remembered that a
few of months ago, while visiting my brother - and after installing xp pro
which converted his W98se machine to dual boot, I'm sure I copied boot.ini
ntldr ntdetect.com and bootsect.dos to disk. So, if necessary, I
should be able to copy those back to the machine. Having said all that, it
occurrs to me that there's nothing wrong with those i.e.
after a cold boot he's getting to boot.ini's dos/dual boot screen and both
platforms, depending on which one he picks, part loads, and then bombs out
with an error message. It's odd though that he ended up with both platforms
broken at the same time !?

Anyway, while attempting to refresh myself with his machine and dual boot,
(until I get to Bournemouth in a couple of days), which I haven't fiddled
with for serveral months, I seem to have become re-interested in it. I
found http://www.cknow.com/vtutor/vtfdiskmbr.htm interesting. And I've
collected some MS "mbr" kb's as well

Annoyingly, I can't find the MS kb page, I saved, that warns that if fdisk
/mbr discovers a problem with the fat's it makes a new one !!!!!

regards, Richard

 

[Alex Nichol]

Much obliged, ...things are gradually dropping into place. This is a
fascinating area of theory, that I'm wading around in at the moment.
While wading around during the past few days, I suddenly remembered that a
few of months ago, while visiting my brother - and after installing xp pro
which converted his W98se machine to dual boot, I'm sure I copied boot.ini
ntldr ntdetect.com and bootsect.dos to disk. So, if necessary, I
should be able to copy those back to the machine.

Doing a Win98 SYS C: is the mistake many then make. That changes the
partition boot sector so it starts looking for the 98 boot files direct
(the XP dual boot uses the code it has saved in bootsect.dos). The XP
files are not affected (though useful to have saved if you did a
reformat) - what you then need is the recovery boot of the XP CD and
fixboot

 

[RJK]

There was me spending hours reading up on some of the inner workings of
W98se / xp pro - including all things dual boot related....because my
brothers machine in Bournemouth would not start up, and I 'phoned my brother
last night and he told me he's switched it on in the morning (yesterday),
and it started up ok. In fact he started it up several times yesterday and
all was okay !!!

So, if I visit this weekend, I'll run his hd maunfacturer's hd diagnostics,
and give the thing thorough checking over from bios settings through every
nook and cranny of his platforms that I'm familiar with, and probably get
his drives configured for some sort of Norton Ghost procedure.

regards, Richard