So out of the blue one of my older, backup drives has gone missing from the HDD list in Windows. When I restarted my machine it said one drive needs to be formatted. I assume the format got corrupted and reset? Is there a way to revert that or do I have to format and loose my files?
This is the second time it has happened, first time I lost my PSD files :/ (different drive, again at least 3 years old).
Sometimes the PC can't read it, try plugging it in a different PC and see if they can read it.
If that doesn't work you might need to format. You can recover files if you manage to see it in the list even if you can't access the HDD. If you see it in the list but can't access it simply install Recuva or other recovery software and recover the files you need.