Re: Boot.ini file help

On Wed, 4 Jul 2007 07:45:12 +0100, "M.I.5¾"

chkdsk does not nomally re-write the MBR. But if you try to check the
Windows system drive (usually C:) or the drive that the swap file is on (if
different), this cannot be done while Windows is running. Hence chkdsk
writes an MBR that causes (or should cause) the machine to boot into a DOS
mode; reboots the machine and runs scandisk. It then reverses the
procedure once scandisk has done its stuff.

No, that's not what happens, even conceptually.

System bootup process...

PSU and motherboard electronic handshake; power on
BIOS POST, processes boot device lists
BIOS loads 1st sector from boot HD (MBR)
MBR code identifies active partition, loads 1st sector of that (PBR)

It is at this point the OS begins. Win9x boot process...

PBR loads C:\IO.SYS
C:\IO.SYS processes C:\Winboot.ini, C:\MSDOS.SYS
If Windows is to be booted, boots Windows
If DOS mode to be booted, loads Command.com and that's it

In contrast, XP's boot process...

PBR loads C:\NTLDR
C:\NTLDR processes C:\Boot.ini
If DOS or Win9x, executes C:\BootSect.dos as if it were PBR
If XP, finds and boots OS via partition syntax


Both Win9x and XP will "fix" the file system if the "dirty" flag is
set, and will do this and then check the HD for surface errors if the
"disk failed" flag is set, but the mechanisms differ.


In Win95/98, DOS mode Scandisk is run during the early stages of boot,
before Windows starts, so that you don't have Windows writing to the
file system that you haven't "fixed" yet. The behaviour of Scandisk
(in this setting) is controlled by Scandisk.ini

In WinME, the DOS mode phase of boot was welded into a solid lump,
which precluded hooks to DOS mode Scandisk. So it launches Windows
Scandisk, and this does get interrupted by Windows writes to disk.
Scandisk.ini still exists, but is ignored; a more limited set of
control can be applied through Scandisk's Advanced options.

In XP, there is no DOS mode OS present, nor is there a DOS mode phase
of the boot process. Instead, AutoChk is invoked to auto-"fix" early
in the GUI phase of startup, and there is no way to control the
behavior of this other than to disable it completely.


Note that in NONE of the above situations does the OS write to or
change MBR, which precedes the OS boot and is thus not a part of the
OS for the OS to change.



------------------------------------ ---- --- -- - - - -
"For every complex question, there's a simple
answer - and it's wrong." H.L. Mencken
------------------------------------ ---- --- -- - - - -
.

Relevant Pages

  • Re: boot.ini editing
    ... If FATxx and HD is < 137G, use a DOS boot diskette with Edit.com on ... don't want to have to boot windows to use it. ... If FATxx and < 137G, you can set a DOS mode as a Boot.ini boot option, ... partition boot loader was present and invoked. ...
    (microsoft.public.windowsxp.general)
  • Re: Invalid Boot Diskette
    ... > partitions and work in dos mode to format my drive. ... but for the last three years I have had Windows XP. ... > boot from my Windows XP CD, ...
    (microsoft.public.windowsxp.hardware)
  • Re: aarGH was NO ROM BASIC, System halted
    ... I did, last night while I was on here, I had started the Windows Scandisk ... Though you may find that it won't run CHKDSK from within windoze ... That was one of the first things I tried, from the Win98 boot floppy, on the ...
    (uk.people.silversurfers)
  • Scandisk will not allow Windows to load
    ... I have experienced an issue where if a scandisk is ... Everytime the system is booted, ... Windows will never load ... boot), but whenever I run scandisk, the same issue arises ...
    (microsoft.public.windowsxp.security_admin)
  • Invalid Boot Diskette
    ... partitions and work in dos mode to format my drive. ... but for the last three years I have had Windows XP. ... now when my PC starts up it goes to a black screen that says, "Invalid Boot ... Diskette- Insert Boot Diskette in A:", but the problem is, I did not make a ...
    (microsoft.public.windowsxp.hardware)