Thanks for your message and excuse me for the confusion. Yes, I must say it can happen - and not rare.
I can confirm that if chkdsk finds problems, it does not really mean that the hard disk is about to fail - and vice versa: if chkdsk finds no problems, it does not mean that the hard disk is perfect.
First of all, chkdsk never finds spin up problems and other issues which are not directly related to the stored data.
Spin up problems are hard to find without proper monitoring: when the drive is spinning, there are absolutely no issues, no slowness, no weird noises, no bad sectors. Just it's possible that the hard disk may spin up harder and harder - and one day it can't spin up (can't start) at all.
Even if this may sounds surprising, chkdsk does not check/verify/repair the hard disk itself, but verifies (and repairs) the logical drive, the partition (logical drive) only.
The problems chkdsk finds (and fixes) are in most cases different than the actual hard disk problems: Windows may find, report and "fix" problems on a perfect hard disk - and may not find anything on an almost failing hard disk.
For example a very frequent cause of chkdsk to find (and "fix") problems if a sudden power failure / power loss occur. This can frequently lead to damaged partition (file system) and cause orphaned files, file000 entries and so - and this can happen even on a perfect hard disk.
Many cases, chkdsk may report problems also when the operating environment is not stable. Power and data cables, connections, drivers are relatively frequent cause of such problems (and even "bad sectors" reported by chkdsk - which are not really bad sectors and may be reported incorrectly even on perfect hard disks).
If you are interested in more details, please check
http://www.hdsentinel.com/hard_disk_cas ... ectors.php
as it shows a relatively common situation when chkdsk detects, reports and "fixes" bad sectors, but they are not actually fixed and they can cause further problems - while Hard Disk Sentinel can really fix the problems - and then chkdsk will no longer reports "bad sectors" of course.
In the current situation chkdsk finds no problems. But this is not surprising, this is exactly what we expect from it.
The "bad sectors" reported by Hard Disk Sentinel in the text description are no longer used by the hard disk: they are already reallocated.
It means that the hard disk moved the contents of these sectors to the spare area and now (instead of the original sector) the spare area is used for all reads and writes targeting those bad sectors.
Generally, these sectors can no longer cause problems, as this way you can be sure that the original (bad) area can not contain important data and can't risk data loss. By this reallocation, the hard disk can still usable - even if it's not perfect. So chkdsk will never find / report these bad sectors.
And ideally, if all such sectors found and repaired this way, no other disk testing methods (for example the Disk menu -> Surface test functions in Hard Disk Sentinel) will find problems with the hard disk.
This is why manufacturers (really shame but work this way) "allow" some bad sectors and may not offer warrantly replacement until the error-level threshold reached.
However, if the health is lower and larger amount of bad sectors reported, it may be an indication that other problems, data corruption, data loss may happen in the future. This is especially true if the amount of bad sectors is high (so the health % value is low) and especially if there are other problems with the hard disk drive (for example spin up problems).
In such situations, there is high risk that the hard disk will fail competely before reaching the error-level threshold.
So by using the surface tests in Hard Disk Sentinel, you can verify if the currently used data area is error-free, there are no further errors reported (no weak, damaged sectors, no further problems).
As these tests monitor the complete operating environment (self-monitoring data, temperature, increasing error count and so), verifies retry count, damaged and sectors slower than should, they are more sensitive to problems than other methods, especially chkdsk - which would ignore these.
For more information about these "bad sectors", please click on the "?" next to the text description (the text area describing the issues) and check
http://www.hdsentinel.com/faq.php#health
For more information about the tests should be used to perform complete verification of the hard disk, to reveal and fix possible problems, please check:
http://www.hdsentinel.com/faq.php#tests
And if you run the tests and confirm that now there are no new problems, you can clear the error-counter and restore the health of the hard disk as described on this page:
http://www.hdsentinel.com/faq_repair_ha ... _drive.php
so then Hard Disk Sentinel will report only any future problems (if there will be).
But on any (even minor) new issue, increased error count and decreased health value, I'd perform a complete backup to an other, possibly better hard disk drive.
