Installing Windows NT on a Large IDE Hard Disk

During the text-based portion of the NT installation, it is possible to create
and format partitions. NT installation prior to SP4 uses a generic IDE driver,
atapi.sys , which is not fully compatible with IDE
drives larger that 8 GB. Most NT installation CDs are SP1. With the older atapi driver any of these symptoms can occur :

  • computer hangs during the format portion of setup
  • computer hangs during fat->ntfs conversion process
  • drive takes extremely long time to format
  • Windows NT does not recognize the entire size of the drive

The SP4 and later atapi.sys is compatible with
greater than 8 GB IDE hard drives. The system partition of the drive (where NT
boots) must be installed within the first 7.8GB of the hard drive. The install
partition is limited to 4GB. The partitioning rules Windows NT uses during Setup
are laid out clearly in Windows NT
Partitioning Rules During Setup
. The 4GB limitation is mentioned there and
covered also in int13 limitations.
Windows NT will only be able to access greater than 8GB drives if your PCs
motherboard and BIOS recognizes and supports large HDs. You may have to update
your PC BIOS to get this support.

The installation process with SP1 is:

  • download updated atapi.exe

  • Copy atapi.exe to a blank floppy disk
  • Run Atapi.exe on the diskette and Atapi.sys file will be extracted to the
  • label the disk Microsoft ATAPI Service Pack 4 IDE

  • Start Windows NT install using 3 NT boot disks.
  • When asked if you would like setup to detect your mass storage devices,
    press S so that detection is skipped and you specify a
    mass storage device.
  • When setup list devices found, which should list , press S again and insert the Microsoft ATAPI
    Service Pack 4 IDE Driver
    disk and press ENTER twice Setup will now list
    Microsoft ATAPI Service Pack 4 IDE Driver as an
    installed driver.
  • Continue setup and during the copy phase NT will prompt you for the atapi
    driver diskette.
Remember you can install Windows NT on a system
partition from 1GB to 7.8GB. The rest of the HD must be another partition (s).

The process is slightly different if installing using Microsoft Small
Business Server 4.0 or 4.0a. See Q197667
which is the source for this tip and includes variant for SBS server.

A related issue involves dual-boot for Windows NT and Win95/Win98. Win9x must
be installed on FAT16 (since NT will not boot to fat32) which constraints the
system partition to 2GB.

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