Microsoft made a comical video in ~1991 for sales people or people running computer stores.

Some of the lyrics go:

loads over any DOS on anyone's PC

Source: https://youtu.be/WxC6PytZMqc?t=192

Is this an over-simplification/lie, or was that really accurate?

Did MS-DOS 5 Upgrade really upgrade any DOS on any PC? Even MS-DOS 1.0 directly to 5.0 on the first PC ever made? If so, that's very impressive.

And did it also include all the non-MS "DOS" OSes? That would be even more impressive.

(Also, bonus points if you can tell me whether there was a "non-Upgrade" edition of MS-DOS 5, because they never mention this at all.)

  • 4
    Better asked on retrocomputing.stackexchange.com Sep 12, 2022 at 13:28
  • The term PC here stands for IBM PC only. So its no big surprise that it would work on any PC. It wouldn't have worked on my CPM, MPM, PET or Apple computers. And it was a clone of CPM. Sep 12, 2022 at 13:31

4 Answers 4


The MS-DOS 5 Upgrade would have really upgraded any DOS on any PC.

This would be done very simply : By replacing whatever operating system already existed on the computer.

  • Okay? Preserving all files and settings, with no new bugs, I presume?
    – Nordholm
    Sep 12, 2022 at 17:00
  • 1
    MSDOS was basically just one folder, the equivalent of C:\Windows today. The settings, as far as I know, were in a couple of files in C:\ .
    – harrymc
    Sep 12, 2022 at 18:42

What you are surmising was a Microsoft internal project, it it existed.

I used DOS 1, 2, 3, 4, 5, and 6 and have a DOS 6 system here.

Each version was separate and did not include other versions.

"Upgrades" consisted of installing the new version. That worked from version 2 forward.


Here is the file structure of a working DOS 6 machine (DOS 6 and prior TREE command). All the DOS program file are in C:\DOS and its subfolders, and there are other important directories as well but you can see how easy it is to upgrade to the next version.

Directory PATH listing for Volume PCDOS_6
Volume Serial Number is 2C58-000E C:.

│   ├───SYSTEM
│   ├───DATA
│   └───HELP
│   ├───ProgLIB
│   ├───MISC3LIB
│   ├───MISC2LIB
│   ├───MISC1LIB
│   ├───LIBS
│   ├───INCLUDE
│   ├───FTLIB
│   ├───EXPER
│   └───CLIB
│   ├───COMIC
│   └───MJVGA
│   ├───NETPROG
│   ├───DRIVERS
│   │   ├───DOSUTILS
│   │   ├───PROTMAN
│   │   ├───NIF
│   │   ├───XIF
│   │   ├───ETHERNET
│   │   │   ├───ELNKII
│   │   │   └───PCNTND
│   │   └───PROTOCOL
│   │       ├───MSDLC
│   │       ├───TCPIP
│   │       └───NETBEUI
│   ├───SERVICES
│   ├───LOGS
│   ├───NETWKSTA
│   └───ETC
│   └───WKSHEETS
  • I have no idea what you mean by "Each version was separate and did not include other versions." And isn't the point of "upgrading" that it keeps all the data and compatibility?
    – Nordholm
    Sep 12, 2022 at 16:59
  • I have upgraded DOS and files are in a non-DOS folder so are saved. There were no compatibility problems in my recollection. Finally each DOS version did NOT contain other versions. Remember DOS was very simple
    – John
    Sep 12, 2022 at 17:01
  • 1
    Settings as they existed then were INI files or like kept with the app in most cases. DOS was a very simple system.
    – John
    Sep 12, 2022 at 17:21

Yes, you could install MS-DOS Upgrade on top of a none MS-DOS DOS version. I tested that with DR-DOS 3.41 and MS-DOS Upgrade 6. It is also mentioned on the Box that any compatible x86 DOS will work. The other DOS must be pre-installed.

MS-DOS Upgrade will ask you for a folder name in which the new MS-DOS should be installed into. That way you could separate the old none MS-DOS from the new MS-DOS. And to delete the old none MS-DOS there was the DELOLDOS.EXE command.

This means, you can have all Commands of both DOS versions at the same time on the hard drive available. And most, with a few exceptions (like DR-DOS's TASKMAX shipped with DR-DOS 6.x and later) can also be used in MS-DOS. But you can't boot into the other none MS-DOS DOS from the Hard drive after the upgrade. Only MS-DOS can then be booted exclusively. To change this again you have to uninstall MS-DOS, i.e. undo the update or use a boot disk.


To answer your other question, yes there were non-upgrade versions of MS-DOS for every version. You couldnt upgrade, if there was nothing to upgrade from.

Typically, when a new PC was purchased, you also purchased the "full" version of MS-DOS. This was a boxed copy, with manuals, other documentation, and of course - the installation floppy disks.

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