I do know about the /f switch...
If I go to Run and enter chkdsk c:/f it will schedule a repair.... and
report no problems on re-booting.
Then use the /r switch to have chkdsk check the sectors are readable.
Rather than just check the file system is okay, it also ensures the data
is readable from the platters. It is not an infallible check. I
believe the OS will permit up to 5 retries to read a sector before
saying there is a problem reading from it, and hard disks may permit up
to, say, 3 retries before reporting an error, so it could be 15 retries
total of which it could take only one, like the last one, to get the
data to pass the test.
SpinRite is a better low-level sector test utility but it isn't free.
What users don't realize is that retentivity of a sector wanes over time
unless its data is read and rewritten. The dipoles to record the data
are under magnetic stress and will alter alignment over time. If
magnetic data, which includes the file system, is not exercised, it will
lose its ability to be read. Microsoft has never provided a utility to
read and rewrite all bits in every sector on the hard disk. They also
provide poor utilities to determine the reliability or retention of a
sector's area on the hard disk, and sectors can lose retentivity over
time either because of non-use (dipolar shift) or due to manufacturing
defect or degradation. However, the time for such degradation (physical
or magnetic) is usually many years and users often replace their hard
drives before those problems show up by getting a new computer (and new
drives versus migrating the old drives into the new host) or getting
bigger drives.
So try "chkdsk /r" first. Also, I gave up on relying on Norton's Disk
Doctor a long time ago, but then I haven't used Norton products for
several years now. When NTFS v5 came out that Disk Doctor would start
reporting non-existing problems was when I gave up on it. They might've
fixed it since then but I never felt it was a reliable repair tool. You
didn't mention WHICH version of Disk Doctor that you are running or from
what version of whatever Norton suite it came bundled. Maybe what you
are trying to use is simply too old and unusable. I'm not specifically
trying to promote SpinRite but instead feel that Disk Doctor is too
lightweight a utility to fix any real [physical] problems on a hard
disk. In fact, I wouldn't be surprised if "chkdsk /r" was about as much
as Disk Doctor could itself perform.