GNU GRUB 0.97 - rootnoverify (hd0, 14) fails w/Error 25 (WORKAROUND)

[Russell Ruby]

System:  Slackware 11.0
         Using "stage2_eltorito" bootable GRUB CD per MANUAL instructions
Hardware:  2006 Compaq laptop
Target Disk:  120GB internal having 15 partitions

Description of problem:

# Goal is to boot the WinXP partition /dev/sda15.
# Boot the GRUB CD, and at the "grub>" prompt,  if "rootnoverify" is
# given any logical partition as a device target, the "Error 25" is
# generated.  However, if "rootnoverify" is given a device target
# a rootnoverify having as device target *any* of the four partition
# entries defined directly in the MBR, then a following rootnoverify
# using a logical partition target succeeds !
# NOTE: the target disk was partitioned with "sfdisk" using the
# "--DOS-extended" option since it was observed that for logical paritions
# the native # WinXP fdisk uses relative sector offsets to the beginning of
# the primary Extended partition container.  (However, unlike cfdisk and
# WinXP fdisk, which both make a chain of disjoint extended partitions,
# sfdisk with the --DOS-extended option makes *nested* extended partitions.)
# I did not experiment to see if a "cfdisk" partitioned disk or sfdisk without
# the --DOS-extended option failes in the same way.  Whatever, but GRUB is
# getting confused by something.

Examples: (these are verbatim transcripts from GRUB)

grub> rootnoverify (hd0,14)

Error 25: Disk read error

grub> rootnoverify (hd0,3)       <---   no error response here...

grub> rootnoverify (hd0,14)      <---   hmmm, no error this time !

grub> chainloader +1

grub> boot                       <---  successfully boots !!

# Above boot into WinXP is now successful using /dev/sda15 !
# Or, below the steps in my current Grub menu entry to avoid
# the Error 25 and successfully boot into WinXP:

title WinXP on sda15 partition
rootnoverify (hd0,3)
rootnoverify (hd0,14)
chainloader +1


Here is an sfdisk -l -uS listing of the target disk:

Disk /dev/sda: 14593 cylinders, 255 heads, 63 sectors/track
Units = sectors of 512 bytes, counting from 0

   Device Boot    Start       End   #sectors  Id  System
/dev/sda1            63  33206354   33206292  83  Linux
/dev/sda2      33206355  84726809   51520455  83  Linux
/dev/sda3      84726810  86333309    1606500  82  Linux swap
/dev/sda4      86333310 234436544  148103235   f  W95 Ext'd (LBA)
/dev/sda5      86333311  93562559    7229249  83  Linux
/dev/sda6      93562561  95972309    2409749  83  Linux
/dev/sda7      95972311  98382059    2409749  83  Linux
/dev/sda8      98382061 104004809    5622749  83  Linux
/dev/sda9     104004811 112840559    8835749  83  Linux
/dev/sda10    112840561 116053559    3212999  83  Linux
/dev/sda11    116053561 118463309    2409749  83  Linux
/dev/sda12    118463311 168007769   49544459  83  Linux
/dev/sda13    168007833 181695149   13687317  83  Linux
/dev/sda14    181695213 201230189   19534977  83  Linux
/dev/sda15    201230253 234436544   33206292   7  HPFS/NTFS