[CentOS] Re: Need Dual Boot Installation Help

[Bryan J. Smith]

duffmckagan <mckagan at gmail.com> wrote:
> Moreover, you can still get that GRUB installed to the MBR,
> then get the Cent OS working, and then patch the Kernel to
> include NTFS Modules. Then add the required lines to the
> /boot/grub/menu.lst file and get windows working.

You do _not_ need NTFS support in GRUB to boot Windows.
GRUB will merely use the chainloader to pass off boot to
the NTFS partition, even though it can't read it.

BTW, note there are _issues_ with GRUB and Windows NT5.1
(XP) Service Packs / Hotfixes.  It seems that on its bootable
drive (what MS calls the "System Drive") on a "Basic Disc"
(legacy BIOS/DOS Primary/Extended/Logical disk slicing), it
uses portions of the MBR to store "hidden info."  It will
overwrite portions of GRUB.  If you re-install GRUB, it will
overwrite portions of these hidden areas, and XP
SP1+hostfixes or SP2[+hotfixes] will not boot.

The conditions seem to vary from system to system, but I have
run into it regularly now -- especially with many SP1
hotfixes and definitely with SP2.  There also seem to be some
conflicting hotfixes, especially SP2+, that constantly change
things (even on a 100% Windows XP system).  If I had to
guess, and based on my views of the MBR with a hex editor, I
think Microsoft is still trying to be compliant with the new
ATA48 spec (lont story).

But _regardless_, I find that by keeping my "system drive"
(C: filesystem) with the NTLDR, BOOT.INI, etc... XP partition
within the first 32GiB (at least when geometry is <4096
cylinders, =255 heads and =63 sectors) of the hard drive will
typically work.

I literally had a situation where XP SP1 was booting fine in
the first 64GiB, then I loaded some hotfixes, and it refused
to boot.  Sure enough, upon inspection of the "damaged"
(non-GRUB booting) MBR (which I made a copy of before
re-installing, and then losing the ability of chainloader to
work), I noticed the same bytes as SP2.



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