So after the massive trouble of finding a 5.25" floppy drive and a connecting it up, then changing the BIOS so it's set as my A: drive, I tried to format a couple of high-density 1.2MB floppy disks using the "format A:" command in Command Prompt. Both times it formatted only 160KB and left it at that. If I then check the amount of space on those disks, it then comes up as 160KB. Why is this the case? How can I get my the full value out of my 1.2MB?

For reference, I have a Mitsubishi MF504C-318UG, which should support 1.2MB disks.

  • 4
    That's fantastic. What are you using a 5.25" floppy for? May 14, 2011 at 21:16
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    I have a huge box full of them I got for free, and I've always wanted to try vintage OS's like Windows 2.0, so I thought I might as well use them as boot disks.
    – Sputnik
    May 14, 2011 at 21:20
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    this almost brought tears into my eyes. Good old days :)
    – Bora
    May 14, 2011 at 21:28
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    I agree with Fahad, XP is a problem. I would boot off another OS to format them.
    – Joe
    May 15, 2011 at 0:35
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    You might want to set at least one tag to say what platform or operating system you're on. Lots of old systems used 5.25" floppies and used different formats. May 15, 2011 at 11:56

7 Answers 7


Try using the /f:1200 command line parameter on the format command.

Well, that is what I did back in my time on MS-DOS.

  • Unfortunately it doesn't work :(. According to this page (support.microsoft.com/kb/309623) it should be possible to format the disks but it doesn't give the command required.
    – Sputnik
    May 14, 2011 at 21:38
  • @Fahad Does your drive has the corresponding three-mode driver installed? What is the OS?
    – Bora
    May 14, 2011 at 21:43
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    Although I'm not sure what that is, I don't think it does; it is just a standard 1.2MB 5.25" floppy drive. The OS is Windows XP.
    – Sputnik
    May 14, 2011 at 21:48
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    Make that /f:1200 (add a colon). Format a: /f:0 may display all valid format types
    – Linker3000
    May 14, 2011 at 21:54
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    I would skip the driver hunt and head right into booting into some Linux. Most Live-CDs are able to cope with floppies successfully.
    – Bora
    May 14, 2011 at 22:21

Microsoft has removed all options from the command line format command /F: parameter in Windows XP except for 1.44. I don't see any good reason for them to do this except perhaps to save money on support calls. However Windows will still read and write to other size disks that are already formatted. I struggled with this one for a while, however I found that you can format other size disks in Windows XP from the command line. The track and sector parameters are still supported! So to format a 1.2M 5.25" floppy simply type:

format A: /T:80 /N:15

You should be able to format any size disk supported by your drive and BIOS by specifying the correct track and sector count.


It depends on the OS, so I'm going to explain the way I did it on Windows XP, which cannot do it 'out of the box' (pre-XP versions all have this capability through 'format' in Command Prompt).

You need to download OmniFlop, then follow the instructions in the User Guide to replace your current floppy driver with the OmniFlop driver (you will not need the OmniFDC driver; that's only for very old, very specific data types).

Open the OmniFlop program, click 'Format Disk', choose your floppy drive (A: or B:), and select the disk type. DOS 360KB and DOS 1.2MB are the most common; these are double-density and high-density respectively. Wait for the progress bar to finish, then you're all done!


Although I don't have a floppy disk handy, have you tried simply right clicking on the floppy drive and clicking "format"? Similar to how you can format memory sticks, etc. That to me would seem to be the best option. You could also try Windows Partition Manager, it may help.

  • I tried this and while it does come up with a window, it simply does not execute the format no matter how many times you click 'format'. As I mentioned to Linker above I think it may a problem with XP itself; it appears that you just can't format 5.25" disks without a magic driver!
    – Sputnik
    May 14, 2011 at 22:17
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    You could try booting into a linux LiveCD, particularly one with a GUI, such as Fedora, and then format from there. That might help you out. fedoraproject.org May 14, 2011 at 23:21

Are you sure that you don't have C64 disks mixed in?

As a child, I got the mistakenly ordered 160KB DD Floppies from my parents work, when they were too dumb to order the right ones (HD).

Also, 160KB sounds pretty much like single sided formatting. Have you 2 or only 1 copy protection holes on them? If 2, they could be formatted double sided giving you about 320 to 360KB. (1541 could not do that on my C64, 1571 on a 128er could).

  • 160 KB is the default formatting size if there is no special driver installed. And this has nothing to do with the diskette being single or double sided. You have to format each side of a double sided diskette separately, anyway.
    – Bora
    May 15, 2011 at 11:44
  • I didn't know 5 1/4" disks came in 1.2MB I thought only 3 1/2" were available in that capacity.
    – dghughes
    May 15, 2011 at 15:14
  • @dghughes: 3.5" come in 740KiB and 1440KiB (referred to as 1.44MB HD) - plain 2Megs, there are also (rare) ED with doubled capacity.
    – mbx
    May 15, 2011 at 15:26

There are some jumpers on the drive that will affect the capacity as well, see this page for the correct settings: http://support.dell.com/support/edocs/dta/procom12/00000001.htm


  • 1
    that is some seriously oldskool graphics
    – Journeyman Geek
    Dec 1, 2012 at 11:55

NO WINDOWS ERRORS on file system to format 5.25" floppy disk. The new Windows drivers cut this possibility. Please, replace "flpydisk.sys" on the SYSTEM32 of XP SP2 and SP3 with older version from XP SP1.

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