Windows NT 3.1 October 1991 build

The October 1991 build of Windows NT 3.1 was compiled for the COMDEX/Fall '91 trade show in Las Vegas. Customary to most officially released Windows builds of the era, this build has all mentions of the build number missing from core system files. Similarly to the September 1991 build, many about dialogs display "Version VERSION" as a placeholder while  only shows "Windows NT version 3.2". Version numbers of SDK tools suggest that this release is based on build 205. The disc and the operating system itself have been updated to use the final variant of the new Windows flag logo.

This is the first known build to include an NT-based setup, and is one of few available early Windows NT builds (besides build 239, at least) to include a fully graphical setup on compatible hardware, a feature which wouldn't return until Windows Vista. It is also the first known build to use the  boot loader, as opposed to the earlier loader used in the September build. The new loader identifies as version 1.5 in this build, which suggests that it has been under development for a longer period before its inclusion.

Under emulation, and presumably on physical hardware, there is an issue with CD-ROM media changes that cause the File Manager and/or Command Prompt to hang. Notably, this build already had long filename support, but only under HPFS partitions. Password authentication doesn't work in this build yet, and the user cannot shutdown in Windows (so to shutdown, the user must power off the machine). Unlike the September 1991 build, this is the first build to have the BSOD as in later builds of Windows.

System requirements
This build requires at the very least the following configuration:
 * 16 MB of RAM
 * COM1 port enabled
 * Prepartitioned and preformatted disk in MS-DOS

Additionally, in order to use the GUI setup, it is required to use a SCSI CD-ROM drive connected to an Adaptec AHA-1540 or compatible adapter.

Supported hardware
This is a list of supported hardware as listed out in the setup:

Computer

 * Compaq 386/486 or 100% Compatible
 * IBM PS/2 or 100% Compatible

Display

 * VGA
 * Video 7 VRAM II (800x600 16 colors)

Mouse

 * Microsoft Mouse or 100% Compatible

Keyboard

 * Enhanced 101 or 102 Key

Additionally, a SoundBlaster 1.0 or 1.5 is supported, but its configuration is hardcoded to I/O port 0x260 and IRQ 7.

Installation
This build can be very picky on hardware, and will usually crash on startup if the right configuration isn't used. As of now, this build performs the best in 86Box, but can also work on VirtualBox, PCem, and QEMU. If installed in PCem, the keyboard won't work.

GUI Setup
In order to use the GUI setup, the system must have a CD-ROM drive connected to the SCSI bus. This has been confirmed to work in VirtualBox and 86Box.

VirtualBox instructions

 * 1) Make a virtual machine with 500MB hard disk and 24 MB of RAM. Use the NT4 profile.
 * 2) Go to VM settings and open the Storage tab.
 * 3) Remove the CD drive from the IDE bus and add a SCSI bus.
 * 4) Add a CD drive this time to the newly created SCSI bus, mount the 10-91 ISO file. It's recommended to set the SCSI port to no. 2, as it's the default boot option on the NT boot floppy.
 * 5) Add a floppy bus and add a floppy drive. Mount an MS-DOS boot disk with FDISK and FORMAT.
 * 6) Go to the Serial Port tab in VM settings and enable the COM1 port.
 * 7) Save the settings.
 * 8) Start the VM. MS-DOS should boot. Run FDISK and partition the drive. Then format it with the FAT filesystem.
 * 9) Mount the boot.img image file and press Right Ctrl+Del
 * 10) OS Loader boot menu should be displayed. Choose the SCSI port of your CD drive you configured in VM settings.
 * 11) Follow the on-screen instructions.

86Box instructions

 * 1) Create a virtual machine with the following config:
 * 2) *Machine: Award 386DX, 16 MB memory
 * 3) *Display: VGA
 * 4) *Input devices: Microsoft 2-button Mouse (serial)
 * 5) *Ports: Serial port 1 and 2 is enabled.
 * 6) *Other peripherals: SCSI: Adaptec 1542CF (enable BIOS in its configuration).
 * 7) *Hard disks: Create a 512 MB hard disk and connect it to SCSI ID 0.
 * 8) *Removable devices: Set the first floppy drive to 3.5" 1.44M and set the first CD-ROM drive to SCSI ID 2.
 * 9) Start the emulator with a MS-DOS boot disk image which includes SCSI CD-ROM support mounted in the floppy disk drive. Run FDISK and reboot. Format the hard drive.
 * 10) (If you do already have a boot disk image for this build, head directly to step 6). Mount the Windows NT October 1991 CD image and create a new 1.44 MB Floppy Disk image in 86Box (Right-click the floppy icon and click "New image...").
 * 11) Browse to the "setup" folder on the CD drive, then run this command: "MAKEDISK boot A:". This will write the boot disk for this build.
 * 12) Keep the floppy disk image you just created mounted in the drive and reboot.
 * 13) On the OS Loader menu, select "NT CDROM SCSI ID 2". The build installer should then boot.
 * 14) Follow the on-screen instructions.

Demo applications
This build includes several demo applications for demonstrating the new operating system abilities.

Win Bez
Demonstrates the Windows NT Graphics Device Interface (GDI), the API responsible for rendering graphical objects on the screen.

Performance Meter
Measures the performance of the then-new NT kernel.

PlayIt
Illustrates the sound and music abilities of Windows generally. A version was allegedly available for Windows 3.1x Enhanced Mode as well.

Mltithrd
Demonstrates the multithreading abilities of Windows NT.