Technology and retro computer blog

Compaq Portable III

Compaq Portable III

I recently acquired this Compaq Portable III from someone in my local area.  This is the third machine in the series that Compaq produced.  I also have the original Compaq Portable.  This one has a Intel  80286 processor, 640k of ram, a side mounted 1.2mb 5.25" floppy and a 20 megabyte hard drive.  It also has a monochrome LCD screen, which was a major improvement over the small CRT that the previous models had.  These machines were released in 1987.

 Compaq Portable III specifications
Manufacturer    Compaq
Release date 1987
CPU Intel 80286
Speed 12 MHz
Ram 640k (expandable with custom module)
Storage 1.2mb 5.25" floppy, 20meg HD
Expansion Available with external module

1 x serial, 1 x parallel, 1 x RGB out


Compaq/MS-DOS 3.1

When I checked this machine out it was the usual scenario with old computers, it powered up but wouldn't boot as the configuration had been lost.  It didn't come with any boot disks either so I couldn't really do any testing on it aside from seeing some text come up on the screen.  I thought this was good enough.  I felt pretty confident that I could boot it with some MS-DOS 5.25" disks that I already have.  On getting the machine home I tried getting it to boot from a floppy but unfortunately I couldn't  get it to boot (more on this later!).

I tried several 5.25" MS-DOS boot disk that I have but none of them would work.  The drive light would come on as expected to scan the disk but the screen would just repeat the "missing system disk" message.  This was disappointing as I started to think the floppy drive was faulty.  I proceeded to take the back cover off, there's six Torx screws holding the back cover on, once removed it comes off quite easily.  Removing the back cover exposes the motherboard and allows removal of the drive cover which exposes the drives.  I could see there was a hard disk installed as well as the floppy.  With the removal of one more Torx screw the drive assembly can be pulled out of the machine from the side.  I tried plugging in a 3.5" floppy drive and booting from that but that didn't work either.

Floppy drive gotcha!
After doing some online troubleshooting I discovered that to engage the floppy disk head you need to put the disk in until it clicks then press the eject button in.  This engages the head onto the disk.  This was quite a discovery because I realised that I wasn't engaging the disk properly on previous boot attempts.  Once I followed the correct procedure for inserting the disk, the machine booted as expected.  I was also able to examine the C drive which proved that the hard disk was working fine.

Compaq III setup
In my reading about this machine I also discovered that unlike other pc's it doesn't have a BIOS setup in ROM.  The only way to configure the BIOS is via the Compaq setup utility which comes on disk.  You can find the setup disks online but unfortunately they come as an extremely annoying exe file package.  There are two versions of this package, one to create 360k 5.25" boot disks (, and one to create 720k 3.5" boot disks (  But are your ready for this, the 360k exe file is 550k in size, so you can't just copy it to a 360k disk.

I managed to use DOSBox on a modern pc to run the main exe, this looked promising as I'd hoped it would extract the utilities which I could then simply copy to a disk.  But no, running the initial exe just extracts some files which then must be run to create the physical disks.  I tried doing this on my IBM 5150 but it wouldn't work.  The Compaq utility wouldn't recognise the floppy drives on the 5150, very annoying.

After some searching online I was lucky enough to find a site where the setup utility files had been extracted from the irritating Compaq archive and made into a 720k disk image.  I was able to use WinImage to easily extract the files and put them on a 5.25" disk.  Once I did this I was able to run the setup utility on the Compaq III and configure the hard drive and other BIOS settings.  For anyone else who needs these utilities here they are in a simple zip.

These are the files contained in the 720k version of the setup disk.  The utilities can be separated if you need them on a smaller disk: (384.43 kb)


The physical condition of this machine is great, after a good clean up it's come up in mint condition.  The only exception being the curly keyboard cable.  These are notorious for decay and mine is no exception, the shielding on the curly cord is crumbling, so that will need to be fixed at some stage.  But aside from that this machine works perfectly, I can boot from the hard drive and run applications, the keyboard works well too.

21 Feb 2016 - Compaq Portable III leather carry bag

When I picked up the Compaq portable III a few weeks ago it came with a carry bag.  The bag was quite dirty and ratty looking but today I decided to see if it would clean up.  On closer inspection the bag is a genuine leather Compaq carry bag.  I gave it a good clean with leather cleaner and conditioner.  I also polished up a few scuff with leather shoe polish.  The bag came up looking really good.

Comments (10) -

  • Marco

    8/02/2016 6:26:36 PM |

    hi I'm marco from Italy,compliment for your collection . Recently i've bought a compaq portable III. i've downloaded your zip files, but i don't own another  pc with 5,25 drive to write the image disk. i know I can replace the drive Inside the compaq with 3,5 and use it to boot, but i'm afraid to break everything. Is it possibile to buy from you a physical copy of diagnostic and DOS 3.31 5,25 disks ( i'll need also a copy of laplink or similar but I would not ask too much) I know the cost of spedition it'll be high.

  • tkc8800

    8/02/2016 7:12:21 PM |

    You can't just plug in a 3.5" drive because you need to configure the machine for a 3.5" drive first.  You need to boot using a 5.25" disk.  I'm in Australia, a long way from you.  Best to find someone in your local area that can make a 5.25" MS-DOS boot disk, then just copy the contents of the zip file to the disk.

    • Marco

      8/02/2016 7:43:45 PM |

      Ok I'll try or I'll buy an old pc msdos with 5,25" drive. Thanks a lot for your files.

    • cygeus

      11/06/2016 11:50:05 PM |

      In fact you can, just (low-level) format a 1.44mb 3.5” floppy as 360kb 5.25” floppy. I used ImageDisk [0] with settings:

      sectors / track = 9
      tracks = 40
      Double Step = On
      Start Sector Number = 1
      Data rate = 300 kbps
      Encoding = MFM
      Sector size = 512 bytes / sector


      • Theo

        14/06/2016 9:30:42 AM |

        Thanks for the info, that's a great solution for creating system disks where all you have access to is a 3.5" drive.  I'll try it out at some stage.

  • Paul Ponsford

    27/08/2016 9:09:57 PM |

    Hi ,
    I purchased a Compaq III portable for $40 about 25 tears ago. For many years it would boot to hard drive with no problems.  I have all the MSdos setup disks and a ms-dos startup disc plus Compaq user programs all on 5.25 inch floppy. but now the onboard battery has died and I need a Compaq "diagnostics Diskette" in order to set date and time. (presumably after replacing the onboard battery) Only then can I boot to hard drive.  Can you supply me this disk on 5.25 inch floppy.  I would be willing to pay all costs to you via Pay Pal for such a service.  I would obtain great enjoyment and satisfaction in resorting this computer to it's original state. I have 5.25 inch copies of Supercalc 4 (spreadsheet prog) and Protext (word processing) and Dbase.  If wanted, I can post you these discs, you can then install and /or copy and then post the original disks back to me.  I would gladly do this for free.  Can you help ?
    At the moment I can not even boot from a floppy disk as I am unable to get past "error 163- Time & Date Not Set"
    Paul Ponsford
    Secret Harbour
    Western Australia

    • Theo

      29/08/2016 12:01:45 PM |

      Hi Paul,

      I seem to remember getting the same 163 error when I was trying to get mine working.  From memory you need to run the setup utility on the Compaq Setup disk and set the date and time.  Once that's done it should clear the error.  

      I'm happy to send you the Compaq setup utilities on 5.25" disk.  Send me your address if you can read my email address on this reply or use the Contact form at the top of the site.  Let me know if your Compaq portable has a 1.2mb or 360k 5.25" drive?


  • Maret

    28/08/2016 2:43:45 AM |

    Hi, very interesting article.  

    During a clear out only yesterday, I came across a Compaq Portable III that I forgot was there, did a search on the internet and found you and your article.  Could I ask a couple of things please (firstly I should note here that I know next to nothing about the inner workings of computers, but am keen to have a look at what's on this one, it might bring back memories of when I first went out to work):

    The Compaq powers up and I get the message to insert the Diagnostic disk, press F1, then I get INSPECT, I select that and get the message to run SETUP.  I have no further disks (just the Diagnostic), but see that you have provided the software in a zip format, which is very helpful, so thanks for that.  I suppose my question is, if I can get hold of a 5-1/4 floppy disk and external drive, connect it, say to an old computer (I can dig out an old laptop running XP -- would that do?), then do I simply copy the contents of the zip folder onto floppies, or do I have to format the floppies in a particular format first?  I keep reading about making a boot disk, but I have no idea where to start with that.  At the moment I need to run SETUP.

    I'd appreciate any help at all.  I am really interested to do this and have a play with this.  I will try and get hold on an old manual.

    Thanks for any help and advice!


    • Theo

      29/08/2016 12:34:45 PM |

      Hi Maret,

      All you need is a 5.25" disk formatted with MSDOS that can boot.  You create a boot disk in MSDOS using this command:

      C:>format a: /s

      Once you've created a MSDOS boot disk simply copy the files from the zip above to the disk.  Using that disk you can then boot the Compaq Portable and run the setup utility.

      You will need to be able to access a pc that has a 5.25" disk drive to create the disk.

      Hope that helps.


  • Maret

    28/08/2016 8:41:01 AM |

    I'm waiting to hear from someone in Germany who takes people's data from 5.25" disks and sends it to them as zip files -- but I've asked if he will do the reverse and take the zip files provided above and supply them on 5.25" disks.  I'll post an update here if/when I get a reply.

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