You may also wanna use
Seatools on that drive too as it can usually do a more thorough job, running the SMART and Short DST tests (when available) and the Short Generic. Do not do the Long Generic, Advanced or Fix All tests, as if the drive is indeed on its last leg, those tests will heavily degrade the drive's state to potentially a point of no return. Looking at the SMART data using something like
CrystalDiskInfo will also give a possible look into the drive's integrity.
Of course, it also goes without saying to backup your data ASAP wherever needed if the disk health is compromised.
As Usasma hinted, though, you
may have a rootkit, which will
not be eliminated with an OS reinstall. Just because the error code 11 shows up displaying a hard disk doesn't necessarily mean it's actually a hard disk. Rootkits will establish virtual drives to host hidden partitions that hold their crucial components, and will often alter the system's interpretation of the virtual drive to make it appear more genuine (or nonexistent!). Make sure to follow Usasma's instructions on it to help determine if this is the case or not.
