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I have original Microsoft floppies, unfortunately they appear unreadable. Were stored in protector, in a box, in a dark and dry place for the last 20 years. No dust, moisture or exposure to magnetic fields as much as I remember. They just seem to lost magnetic charge. Provided that's the only thing that happened to them, can I write disk images to them in attempt to restore it (at least for some time) or I'm better of just transferring labels to a brand new, good quality disks?

Microsoft Install Disks

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    Do they appear blank but readable, e.g. formatted? I'd be surprised, I'd expect to find a directory but errors on reading files. I can imagine a disk blanking itself, but I can't imagine a disk formatting itself to FAT! – Mark Williams Jun 4 '20 at 21:55
  • Well, my system hasn't got any OS right now, it just throws disk error press any key to retry. Waiting for USB floppy from amazon, so I can't say with certainty. – Bartek Malysz Jun 4 '20 at 22:01
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    My experience is that if you can rewrite AND verify the floppy from a disk image, then it's good-to-go for another storage round of unknowable duration. – Brian H Jun 5 '20 at 0:08
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Provided that's the only thing that happened to them, can I write disk images to them in attempt to restore it

Yes. However, it's rare for floppies to just "loose magnetic charge", unless they have been stored somewhere where they were exposed to magnetic fields, or other unfavourable conditions that caused this to happen. Though the magnetization does get weaker over time.

What happens more often is that the surface of the floppy degrades (the metaloxide particles that store the magnetic charge get loose to some degree), and then you are

better of just transferring labels to a brand new, good quality disks

The only way to find out is to format the old disks, write all of their sectors, read them back, and see if that works without read errors.

If it does, in most cases the floppy should be fine for longer usage.

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    Even better, format and write the disks, read them back, and read them again a while later (days, weeks, months, depending on the intended use). – Stephen Kitt Jun 5 '20 at 6:21
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    Also, if disks fail, have a look at the read/write head of your drive. If it's full of black gunk after just a few disks, clean it, and throw away the disks. – Michael Graf Jun 5 '20 at 8:40
  • Various devices have been built which record analog voltages from the drive head rather than trying to decode bits in real time. I don't what such devices are presently available, but with the right software it's sometimes possible to recover data from disks which would be too degraded to be read normally. For example, if a section of the disk which is two bit times long is supposed to be polarized in the direction opposite the immediate surrounding areas, the start and end of that section should be reported as flux reversals, while the area between should have no flux reversals. – supercat Jun 5 '20 at 15:51
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    @supercat The question was really about if the disks are still good to use, not if the data on them is recoverable (because the question also mentioned that there are existing disk images for these). – dirkt Jun 5 '20 at 15:53
  • If a piece of oxide in the middle of that region falls off, however, the drive might report flux reversals at the start and end of the missing region, in addition to those at the start and end of the region that should be magnetized. This would make decoding the data via conventional means difficult or impossible. On the other hand, the apparent flux reversals would be smaller than real ones, would occur at the wrong times to be real, and could be seen to be roughly equal and opposite. Software designed to recover data in such circumstance may thus be able to filter them out. – supercat Jun 5 '20 at 15:54
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To make them functional again you need to do a low level format. The floppies looks like they for PC (MS-DOS). In there you could type

Format A: ...

but that is not a valid low level format and will not remedy your floppies. What you need is to use FHFORMAT utility (in MS-DOS). That will remagnetize and restore the surface index data ...

Just take in mind that for most 1.44 MByte floppies the safe data retention is only up to a 1 year.

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