If your BIOS allows choosing which drive you boot from, you could effectively have one drive for each OS and switch from the BIOS setup menu .

Yup, that's a good idea.

Btw, it's also possible to use a mechanical switch for that.

It works if the BIOS is set to autodetect or if both drives are using the same drive geometry.
How it essentialy works is as following: The IDE cable is modified to flip master/slave position.

This way, both drives are bootable and can be threaded independendly.

Link:
http://www.stefanv.com/electronics/ide_dual_boot.html

If that's to stressing, it's also possible to set one's drive to auto
and wire up a switch to the other drive's master/slave/auto jumper block.

The wiring is done in a way, so that master goes to one pin, slave to the other one.
Common ground (-needs to be figured out by using a multi-meter or ohms-meter-) to the switch's center pin.

This is how I imagine it *should* work (in theory, had no chance to try it so far):

You can use a boot manager to do this. I used MasterBooter do to something similar. (Windows 98 and Windows ME on separate drives on the same system. Each thinks its on drive C:)

Errius wrote:

You can use a boot manager to do this. I used MasterBooter do to something similar. (Windows 98 and Windows ME on separate drives on the same system. Each thinks its on drive C:)

Could I perhaps install a similar program to a floppy disk and have it do that same task?

Never tried myself, but I believe Win 3.11 can run from DOS 7.1 with a modified io.sys. If I'm right, another alternative is to add the bootgui=0 line to msdos.sys, build a boot menu in autoexec.bat/config.sys with the needed parameters for the different OS:es, and let W98 and 3.11 coexist on the same drive.

IIRC DOS/W9x refuses to boot from other than the primary master drive in their default configurations, so if you want to run everything completely vanilla, I'd gone with Jo22's suggestion. It can easily be done with a DPDT on-on switch, a few single pin connectors, and some wire.

TheAbandonwareGuy wrote:

Could I perhaps install a similar program to a floppy disk and have it do that same task?

This is how I did it:

1) Physically disconnect drive 2
2) Install first OS on drive 1
3) Reconnect drive 2 and disconnect drive 1
4) Install second OS on drive 2
5) Reconnect drive 1
6) Boot from a DOS floppy and install the boot manager. Configure the OS menus and make sure that drive 1 is invisible to the OS on drive 2. (The reverse is not necessary.)

Not sure if this is helpful, but I'm using a SD to IDE adapter in my retro machine which replaces one of the expansion slot brackets. This means that to change OS I only have to switch out the SD card. Currently dual booting W95 and NT4 so I'm sure it can be done with what you already have.

You know Windows can do this natively right? Just as long as you install each OS in sequence.
Install DOS/Win3x
Install Win98 and select Keep existing system (or something like that)
Install NT4

Only limits are c:\ would have to be a Fat16 drive, but this could be a couple of MB just for the boot files, Not even dos HAS to be installed to c:\
And the MS way doesn't let you duel boot between different DOS's or WIn9x's

You will also need to boot into Win98 just to boot back to Dos and you do need to reinstall all your OS's
So not saying this is the most elegant method, but it can be done without 3rd party tools

Its not self promotion but this is basically what i did in my 3-in-1 pentium build, i have one windows 98 install and one ms dos 6.22 with WfW 3.11.
I did everything using BootIt NG and i made a video explaining how to do it:https://youtu.be/Qz1gQORp7PU
The nicest part is you can isolate partitions(so malware cannot ruin your other partition).
The way i had set up is i have both partititions for the system and one shared partition for transfering file between those.

I've had great success with System Commander 7 and that's what I have on the Pavilion. MS-DOS/WfW 3.11 on a 2GB drive, Windows 95 on another hard drive. Booting managed by system commander 7.

chinny22 wrote:

You know Windows can do this natively right? Just as long as you install each OS in sequence.
Install DOS/Win3x
Install Win98 and select Keep existing system (or something like that)

That's the easiest way to do it. It's not the 100% separation that some like to achieve (Win98 "knows" about the DOS installation), but unless one is a purist, that's not a problem.

chinny22 wrote:

Only limits are c:\ would have to be a Fat16 drive, but this could be a couple of MB just for the boot files, Not even dos HAS to be installed to c:\

Well, not necessarily C:\, but DOS does have to be installed on some FAT16 partition.

On this particular system, I would install DOS (and Win3.11) on C:\. 1.2GB should be enough for it. Then install Win98 on D:\ which would be a 20GB FAT32 drive. Only the boot files need to reside on C:\.

Set BootMulti=1 and BootMenu=1 in 98's MSDOS.SYS and it will present you with a menu to choose between Win98 or DOS every time.