I'm going through a bunch of 1.44 floppies before I throw them out - some seem to register as unformatted - I suspect this may be due to some incompatibilities that I've heard of between formats done under different Operating Systems? Can somebody give an overview of this issue/solutions ?
As much as I know, the only thing that could be different is head level in your floppy drive. After all, floppy diskettes have been a media for distributing drivers for mouses/network cards/whatever, which included drivers for Win98/2000/XP/whatever, so... They could also be unreadable after some time because they "lost" what was written. After all, it is magnetic media... Solution... If it is one of these problems, I guess SpinRite is a solution for trying to retreive what was written, and solution for head level is: open your drive, use a screw driver to screw/unscrew until you get the desireh head level.
I can't speak to how some versions of Windows see a floppy, but I know that back when I used to buy them some came formatted and some didn't. So all things equal, it could just be that you have one that has never been formated.
Like I said though, I can't speak to how different OS's see a floppy without research.
... Some could be formatted for a Mac (which a PC can't read)
... Some could simply have deteriorated and no longer be readable (without special equipment)
... Some could have been created on a drive with a significant head alignment difference from the one you're using (this should not normally be the case with modern soft-sectored floppies; but it's possible)
Why should we stick to "Formatted for Mac" - some diskettes could be formated for Amiga! :-)
To put a joke on a side, if you are sure that those were formatted, and had some information on it (which means that it'd been formatted previously, either bought formatted or formatted manually), there are no difference in FAT in diskettes if it has been used for windows operating system. There was a way to format 1.44 3.5" diskette from dos to 1.6 mb, but as I recall, that was also readable, regardless of Windows version.
