Re: Mbr messed up?
From: Chuckw (Chuckw_at_discussions.microsoft.com)
Date: 08/22/04
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Date: Sun, 22 Aug 2004 13:23:02 -0700
I have a slightly different problem than was reported by Ed but as you know a
lot about the MBR I thought I would ask. I suspect my problem was triggered
by hibernation mode in Win XP as twice something has been corrupted so I
can't boot up at all after coming out of hibernation. I get the message " A
disk read error occurred" on reboot. To fix this I have tried:
1. FIXBOOT and FIXMBR using the Recovery Console with no affect.
2. Reinstall XP in place which results in the same error when it reboots
3. Ran Chkdsk /R with no errors found
4. Looked at the MBR sector which seems to be ok
5. Used a program called BART which enable me to recover my files ok.
There is one article on the Microsoft WEB site which indicates a similar MBR
failure for drives over 137GB and I am using a 250G drive but they only
provides a fix and I need some way to repair the problem so I can boot at
all. My question is does hibernate mode modify either the MBR or boot sector
in order to restore the state of my PC when it comes out of hibernate. Could
this cause the corruption I seem to have? Thanks.
"*Vanguard*" wrote:
> Ed H said in news:eh6QJq8TEHA.3976@TK2MSFTNGP09.phx.gbl:
> > Sorry if this off topic, I can't seem to get an answer from Symantec.
> > Was dual booting XP and XP, tried to format and re-install one, after
> > the first re-boot got a message something about MBR messed up. Tried
> > to boot again, got a blue screen error, crashed. Cleaned everything
> > up, tried it again, uninstalling Boot Magic first, still no go.The
> > only way to get rid of the error was to format both OS's and
> > re-install both. How can I resolve this for future use? If I want to
> > change an OS for another how do I keep Boot Magic from messing up my
> > MBR? And do you know a good link to explain the boot process? Where
> > are these files stored?
> >
> > Thank you,
>
> There are 2 boot programs, one for a hardware boot (after the BIOS POST)
> and another for the OS boot. The bootstrap program is in the first 460
> bytes of sector 0 of the first physcially scanned hard disk found by the
> BIOS. The BIOS loads this bootstrap code. The standard bootstrap
> program reads the partition table to find out which partition is marked
> as active. It then reads the partition table entry for the active
> partition to find out its starting sector. The bootstrap program then
> loads the boot program found in the boot sector (first one in that
> active-marked partition) which is the actual first file opened for the
> operating system. The BIOS loads and starts the bootstrap program in
> the MBR (first 460 bytes of sector 0 of 1st physical hard disk) which
> then loads and starts the boot program in the first sector of the
> active-marked partition.
>
> BootMagic does a little to change this but not by much. It replaces the
> standard bootstrap code in the MBR but the rest of BootMagic must reside
> on a FAT partition. That is, BootMagic is larger than will fit within
> the 460 bytes allocated for the bootstrap code in the MBR, so
> BootMagic's bootstrap program merely knows where the rest of its program
> files reside and loads those. Other boot managers will sometimes usurp
> the unused remaining portion of track 0 for their additional program
> code and/or to extend the partition table beyond its 4-entry limit (so
> you can boot dozens of operating systems) whereas BootMagic keeps all
> that data on whatever FAT partition where it was installed.
>
> Parallel installs of various Windows versions should not touch the MBR
> bootstrap area (unless there is no bootstrap program there). The
> conflict arises in them vying for use of the boot sector in the
> partition in which that operating system was installed. You install
> Windows XP into a partition and it writes its boot program into the
> first sector of that partition. You then install Windows ME and it,
> too, writes its boot program into the first sector of its partition. If
> you install Windows ME into the same partition as where you installed
> Windows XP, the boot program for Windows ME will overwrite the boot
> program that was there before for Windows XP. If you use wholly
> separate primary partitions into which you install Windows XP and
> Windows ME, each will have their own boot sector in their own partition
> and they won't step on each other. Unless there was no MBR bootstrap
> program, neither install should overwrite what is there (notice I say
> "should").
>
> If you get an MBR bootstrap program you don't want, you can rewrite it.
> If you want the Windows XP version of the bootstrap program in the MBR,
> boot using the Windows XP install CD, select the first Repair option
> which loads the Recovery Console into a ramdisk, and run FIXMBR. If you
> want the Windows 9x/ME version of the MBR bootstrap program then boot
> using a bootable floppy that has FDISK on it and run "FDISK /MBR".
> However, although there my be byte differences between these bootstrap
> program versions, I suspect they are near equivalents to each other (I
> don't have copies of each to do a compare on their bytes). In fact,
> some MBR utilities have an option to overwrite the 460-byte MBR
> bootstrap area with a "standard bootstrap program" (don't remember if it
> was MBRtool, MBRwork, or MBRwizard).
>
> Rather than uninstall BootMagic, I believe it has an option or program
> that will restore the original MBR bootstrap code (or maybe it just
> installs what is considered the "standard bootstrap program"). But then
> FIXMBR or FDISK /MBR would probably do the same thing. You give so
> little information regarding what actually happened that it is
> impossible to provide details on how to prevent the same problem(s) from
> arising again. Your description is way too vague to provide
> preventative remedies but then unless you are familiar with the MBR, how
> the system boots, the partition table, and boot programs for the various
> Windows flavors then it gets really hard to remember what all happened
> (unless you keep a writing pad and pen next to your computer to write it
> all down).
>
>
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