Why can't I use the other disk of the mirror set to boot Windows NT?

A. When you create a mirror disk, you automatically create the partition. However, you don’t automatically update the Master Boot Record (MBR) of the disk with the Windows NT boot loader.

To install the NT boot loader, first partition and use Disk Administrator to format the drive, which writes the MBR to the shadow disk. You then delete this partition and continue creating the mirror.

If you already have a mirror disk that you need to boot from and don’t want to use a modified NT boot disk (see Q. How do I create an NT Boot Disk? for details), you can use the repair process to write the MBR record to the shadow disk. To do so, complete the following steps:

  1. Use the three NT installation disks to boot the machine.
  2. After you run the first two disks, the installation program gives you options to choose from. Select R for repair.
  3. Clear the checkboxes for all options except Inspect Boot Sector, and continue.
  4. Press Enter to detect hardware, and insert the third disk.
  5. The repair procedure will ask if you have an Emergency Repair Disk (ERD). Choose Yes, and insert the ERD.
  6. The machine will reboot, and the shadow disk will include the MBR record.
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