Bad Sectors and a Failing (but Working) Drive
A drive that's slow, occasionally throws read errors on specific files, but otherwise still works, is usually failing gradually rather than having already failed — and that's exactly the window where the right response can keep this from ever becoming a real emergency.
What's actually happening
On hard drives, unreadable sectors can result from media defects, head problems, contamination, or other developing faults. The drive may remap unstable sectors to spare locations, and SMART attributes can provide useful evidence, although their meaning is vendor-specific. SSDs expose similar logical read errors, but internally they manage flash pages and erase blocks through a controller, ECC and wear management rather than behaving like a platter with literal magnetic sectors.
How recoverable this really is
This one comes down mostly to timing and distribution of the unreadable areas. Files whose required sectors remain readable may be recovered intact; files that intersect unreadable areas may be partial or corrupt. A growing count of read errors or reallocated/pending sectors is a strong reason to stop treating the device as reliable, but SMART data cannot predict an exact failure date or guarantee that complete failure is imminent.
The general approach
The priority is a full, sector-by-sector image of the drive as soon as growing bad sectors are noticed, using imaging tools built specifically to handle read errors gracefully — retrying selectively, skipping and continuing rather than stalling, reading around damaged areas from alternate directions. Once a good image exists, all further recovery work happens on that copy, and the original drive can be safely retired.
Don't keep the drive in daily use "since it still mostly works," and don't run disk-checking or defragmentation utilities on it. Both add exactly the kind of repeated stress and extra writes that push a slowly failing drive toward a sudden, complete one.
Whether software alone is enough here, or whether dedicated imaging hardware is worth the cost, is exactly the question software vs. hardware recovery tools walks through. See HDD vs. SSD vs. NVMe for how bad-sector-style degradation differs across drive types.
This page describes the general situation, not a guaranteed fix for your specific case. If you'd rather have someone experienced take a look before you try anything, see what a hands-on evaluation looks like.