DOS ain't dead

failed with hybrid MBR under Windows (Users)

posted by RayeR , CZ, 07.05.2026, 15:40

Unfortunatelly my hybrid MBR attempt failed. Crucial problem is that Win7-x64 and XP32 (with W2k3 drivers) recognize GPT only if the MBR contains protective partition type EEh in the 1st partition table entry and the rest of part.table MUST be cleared to zeros. If there's added any other partition or if EEh partition is not located in the 1st entry then Windows just ignore GPT and use MBR instead. Only Linux can read such disk correctly prefering the GPT regardless other partitions in MBR. DOS itself seems has no problem with EEh partition, just ignore it, old fdisk show unknown partition.
I also tried to use GRUB4DOS to subvert GPT MBR image from file to memory when windows boots but it failed when windows loader switch to pmode and vanish faked MBR from memory (and read real one from HDD).

It would be possible to do manual MBR swap at boot but it can easily leave MBR with unwanted version when system crashes and it's not swapped back.

Also there's still 2TB limit in WinXP32 even with W2K3 drivers that was successfully enabled to accept GPT but it failed to access the last partition beyon 2TB to the end while 32b Linux and W7-x64 can access it correctly.

So I'm disappointed. I cannot find any hacked windows drivers. Maybe I could try some IFS or imaging driver that can mount any physical partition according to given LBA instead of partitions provided by system, not sure if such exist...

---
DOS gives me freedom to unlimited HW access.

Complete thread:

• Partitioning of 4TB HDD for legacy OSes - RayeR, 27.04.2026, 22:45 (Users)
  • Partitioning of 4TB HDD for legacy OSes - mceric, 28.04.2026, 01:35
    • Partitioning of 4TB HDD for legacy OSes - bretjohn, 28.04.2026, 03:04
      • Partitioning of 4TB HDD for legacy OSes - Laaca, 28.04.2026, 05:08
        • Partitioning of 4TB HDD for legacy OSes - RayeR, 28.04.2026, 17:28
          • Partitioning of 4TB HDD for legacy OSes - Rugxulo, 29.04.2026, 05:23
            • Partitioning of 4TB HDD for legacy OSes - RayeR, 29.04.2026, 20:09
        • Partitioning of 4TB HDD for legacy OSes - bretjohn, 28.04.2026, 17:30
          • Partitioning of 4TB HDD for legacy OSes - Laaca, 28.04.2026, 18:31
            • Partitioning of 4TB HDD for legacy OSes - RayeR, 28.04.2026, 20:31
    • Partitioning of 4TB HDD for legacy OSes - RayeR, 28.04.2026, 17:21
  • Partitioning of 4TB HDD for legacy OSes - Zyzzle, 29.04.2026, 01:39
    • Partitioning of 4TB HDD for legacy OSes - bretjohn, 29.04.2026, 03:39
    • some TSR/patch to modify BIOS/EDD? - RayeR, 29.04.2026, 20:20
      • some TSR/patch to modify BIOS/EDD? - ecm, 29.04.2026, 20:56
        • some TSR/patch to modify BIOS/EDD? - RayeR, 30.04.2026, 17:31
          • some TSR/patch to modify BIOS/EDD? - ecm, 30.04.2026, 20:06
          • some TSR/patch to modify BIOS/EDD? - Laaca, 01.05.2026, 12:24
          • some TSR/patch to modify BIOS/EDD? - RayeR, 04.05.2026, 17:48
            • failed with hybrid MBR under Windows - RayeR, 07.05.2026, 15:40
              • failed with hybrid MBR under Windows - bretjohn, 07.05.2026, 22:36
                • failed with hybrid MBR under Windows - RayeR, 09.05.2026, 18:16
                  • failed with hybrid MBR under Windows - RayeR, 11.05.2026, 07:47
                    • New Idea how to beak 2TB on WinXP-32 - RayeR, 23.05.2026, 13:51