Formatting a 5.25" floppy disk

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.

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.

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).