WinImage works for writing 720KB images even on Win10, there is something else going on. Of course you need to have the hole covered if you're working with an HD drive. Are you sure that this m/b has a standard floppy controller and BIOS support for DD? I'd boot it temporarily with another OS just to find out.

Probably that is the issue - the moment I cover the hole, if I try to access the drive Explorer crashes and WinImage briefly opens up the "writing disk" dialog which then closes immediately with no errors. I didn't realise I needed BIOS support for 720k.

Meanwhile I think I've managed to use command prompt under Windows 98 - but I was hoping to find a more convenient way.

BTW, this is a 1.44MB disk, I am covering the hole only. I've read ONE comment saying this is not going to work...

I can try a different motherboard for sure. How do I find out if the BIOS has 720K support? The drive is a Panasonic one - I believe I also have a SONY model.

Thank you!

tony359 wrote on 2022-12-16, 09:18:

BTW, this is a 1.44MB disk, I am covering the hole only. I've read ONE comment saying this is not going to work...

This method works, covering the hole of a HD disk in a HD drive is enough.

tony359 wrote on 2022-12-16, 09:18:

How do I find out if the BIOS has 720K support?

A safe way is if it allows you to define the drive as a 720KB one.
But you didn't say what motherboard/platform you are using, if it's not that old it won't give you the option (Still the drive defined as 1.44MB in BIOS should be able to write DD disks on a standard controller)

tony359 wrote on 2022-12-16, 09:18:

How do I find out if the BIOS has 720K support?

A safe way is if it allows you to define the drive as a 720KB one.
But you didn't say what motherboard/platform you are using, if it's not that old it won't give you the option (Still the drive defined as 1.44MB in BIOS should be able to write DD disks on a standard controller)
[/quote]

Sorry! It's a Gigabyte GA-G31M-S2L with a Core 2 quad on it. it's my fastest "old" board, to run Windows 10.
Gigabyte website says it's got an iTE IT8718 for the floppy - which also looks after many other things.

The datasheet of the iTE says it supports 720K

Floppy Disk Controller
− Supports two 360K/ 720K/ 1.2M/ 1.44M/ 2.88M
floppy disk drives
− Enhanced digital data separator
− 3-Mode drives supported
− Supports automatic write protection via
software

So I am assuming it might be the BIOS?

The floppy is a Panasonic JU-257A606P. From the datasheet below I believe it says 720K is supported - I'd also assume that a good brand actual floppy drive DOES support 720K 😀

I can try to see what the BIOS says. Thanks for your help so far.

As I said in the first post, "I'd boot it temporarily with another OS just to find out". Like DOS or a linux live cd, just to rule out some weird software/driver issue, it might be as simple as that.

Shall try and let you know!

The BIOS lists 720KB as available choice so it should work.

Under MSDOS (6.22) if I just format the disk it tries at 1.44MB and fails. I have to manually select 720K via the /F:720 option. Then it seems to be working as I can boot from that disk and it runs MSDOS.

I'll try later if Windows 10 likes it better when I select 720KB into the BIOS maybe.