Windows 3.1 Support for Windows 95

Microsoft included the capability to run Windows 3.1 on top of Chicago (Windows 95's development name during Beta days). They said about it themselves:

Chicago can run Windows 3.1 on a separate screen, if you wish.

Well, let's do that!

This project is meant to document this lost capability, which never made it to the Windows 95 final release, and provide a means to install it to Windows 95, yet even Windows 98 (and, somewhat, Windows Me), to try it out yourself.

What is it?

Microsoft speaks about running Windows 3.1 in a VM, technically speaking a Virtual DOS machine.

This is achieved basically by four files:

• win31.exe, a custom loader application (similar to win.com), specifically to make Windows 3.1 run on Windows 95
• win31.pif, a PIF file for said loader
• dualmous.drv, a mouse driver tailored to run conflict-free within the VDM
• dualcomm.drv, a serial driver tailored to run conflict-free within the VDM

Which releases are available?

Microsoft included this capability in Chicago builds 81 to 328.

This repository includes just the version from build 116 and build 328, although they differ not too much from each other.

The main difference is the "switch-back" icon, that is used to return to Chicago/Windows 95. Build 116 refers to "return to Chicago", while build 328 refers to "Return to Windows 95". Accordingly, the icons have been changed.

System Requirements

• Windows 95 RTM, or Windows 98/SE RTM
• Windows Me RTM is also possible, but the mouse is not working
• Windows 3.1 or 3.11 must be installed to your hard drive side-by-side to Win9x
• Windows for Workgroups 3.1/3.11 is also fine
• Windows 3.0 is not supported

Installing Windows 3.1/3.11

Unless you have Windows 3.1x already installed, you can still install it from within Windows 9x, but you must exit to MS-DOS mode.

• run lock c:
• run setup.exe from the Windows 3.1x install media
  • chose to install Windows 3.1x to a new directory (do NOT, I repeat, do NOT, install it to your current C:\WINDOWS directory!)
  • when asked, deny Windows 3.1x to change CONFIG.SYS and AUTOEXEC.BAT, you won't need any changes to these files at all!
• run unlock c: once setup has completed
• then exit from MS-DOS back to Windows 9x

Note: Windows Me doesn't have MS-DOS mode any more. But you can restore that using this community patch Follow the procedure outlined above.

Installing this Distribution

An INF installer is provided for your convenience. This will install all relevant files beneath C:\WINDOWS\SYSTEM\WIN31.

A Readme file and direct links to the release 116 and 328 directories will be added to the Startmenu.

Please follow the additional instructions in the Readme on how to make it work.

Removing this Distribution

This package registers with the Software catalog, so you can easily remove it again via Control Panel -> Add/remove programs.

NOTE: This will only remove the support files, but not your Windows 3.1 installation residing elsewhere on your hard drive.

Excerpt from original Windows Chicago Beta Release Notes

The following excerpt has been taken from the Chicago Beta 1 release notes, dated 5/31/1994.

This is how Microsoft described to use the feature back then.

Windows 3.1 running in a VM

Chicago can run Windows 3.1 on a separate screen, if you wish. Note that the applications will have to be installed separately for Windows 3.1 and Chicago in this case.

You should only run Windows 3.1 in VGA mode (640 x 480, 16 color). The reason for this is that many Windows 3.1 video drivers require the presence of a separate Windows 3.1 VDD. The VGA driver does not have this requirement and so it functions correctly on the Chicago VDD. The ability to run on other drivers depends on their requirements. It may or may not succeed.

To run Windows 3.1 under Chicago

1. Copy the file WIN31.EXE from your \CHICAGO\SYSTEM directory to your Windows 3.1 directory (usually C:\WINDOWS).
2. Edit the following lines in the file SYSTEM.INI in your Windows 3.1 directory (usually C:\WINDOWS\SYSTEM.INI):

Change To

COMM.DRV=COMM.DRV	COMM.DRV=C:\CHICAGO\SYSTEM\DUALCOMM.DRV
MOUSE.DRV=MOUSE.DRV	MOUSE.DRV=C:\CHICAGO\SYSTEM\DUALMOUS.DRV

Do this only if the original lines accessed the COMM.DRV and MOUSE.DRV files (the right side of the "=" sign). 3. Set the Command Line and Working Directory in the WIN31.PIF file to reference your Windows 3.1 directory, if it is something other than C:\WINDOWS. To access these properties: a. Right click on the file C:\CHICAGO\SYSTEM\WIN31.PIF b. Choose Properties from the context menu c. Choose the Program Property Sheet d. Make sure that the Command Line entry starts with your Windows 3.1 directory. Make sure that the Working Directory entry is your Windows 3.1 directory.
4. In your Chicago Main group, create a link to the file \CHICAGO\SYSTEM\WIN31.PIF.

To access Windows 3.1, double-click the icon you just created. Please do not perform Control Panel-related operations from Windows 3.1. However, you can run any application from the Windows 3.1 screen and it will run in a Windows 3.1 environment. To return to Chicago, click on the Chicago icon that will be visible on your Windows 3.1 screen.

Known Issues

Mouse not working on Windows Me

Mouse works fine on Windows 95 and Windows 98, but not on Windows Me.

There is currently no known solution to this.

Control Panel segfaults

That is a known error since the early beta days, and was never resolved.

MS-DOS Prompt can be started

That is a known error since the early beta days, and was never resolved.

Build 115 binaries locks up or crashes Windows Me

This was observed multiple times. Try the build 328 files instead, these seem to work.

Why are other builds not included?

This feature didn't seem to receive significant improvements over the course of Windows Chicago's beta run.

The only significant change was that at some point, the program icon and the label to it shown in Windows 3.1 where changed from "Return to Chicago" to "Return to Windows 95".

Do I really need to copy the files to the Windows 3.1x directory?

Yes. It's not sufficient to just point the PIF's working directory to the Windows 3.1x path. You must have them residing in the Windows 3.1x directory or it won't work.

Technically speaking, the two .DRV files don't need to be there, as you could point the full path to them in SYSTEM.INI.

But to simplify things, I went the easy route, just copying everything into the same spot. Follow the README as it tells you.

I thought these binaries wouldn't run on the final Windows 95?

That's true.

In order to make them run, both versions of WIN31.EXE have been patched at offsets 0x360h and 0x827h. The Op-Code 74 was changed to EB to bypass the version checks.

Original code segments:

83 F8 04			cmp	ax,4
74 10				je	$+12h

change to

83 F8 04			cmp	ax,4
EB 10				jmp	$+12h

and

3D 04 00			cmp	ax,04
74 0B				je	$+12h

changed to

3D 04 00			cmp	ax,04
EN 0B				jmp	$+12h

Acknowledgements, Copyright

This is original application binaries provided by Microsoft, and thus subject to their Copyright, (c) 1981,1994 Microsoft Corp.

Strictly speaking, it's not allowed to redistribute these files. The motivation lies in documenting an interesting technological feature, making it available to the retro community and tech enthusiasts, for the sole purpose of showcasing historical software capability and it's behaviour.