Help explain this behavior - uncorrectable sector count


One day i noticed ONE “uncorrectable sector count” and ONE “Pending sector count” in SMART on my WD 640 GB HDD.

When i run HDTune’s error scan i got bad block on “55769” MB location. Then i backed up system partition using clone zilla and reformated whole system partition(full format). I have done bad sector scan on whole HDD after that and none BS were found. Restored partition, booted Windows normally, and opened HD Tune. No bad sectors were found on “55769” MB location. “Pending sector count” in SMART decreased to 0, afted that but “uncorrectable sector count” remained on ONE sector.

There are no realocatated sector.

How is that possible?

Why there is no bad sector on that location on disk now, if that sector was real uncorrectable sector?

If that sector was fake [Deleted - Trancer] why didn’t it go away after format and why SMART still says there is one uncorrectable sector?

Where did that sector go if there is no bad sector on that location on HDD now and “realocatated sector count” is at 0?

You were provably getting a bad reading from HDTune, you can try running a DLG test for a second opinion. Check the link below for the steps. 

How to test a drive for problems using Data Lifeguard Diagnostics for Windows

I’m not getting a bad reading from HDTune. Unreadable sector was present before formating. Now it’s gone, and my question was:

“where it went since it’s not reallocated?” and

"Why is there uncorrectable sector in SMART and disk reads 0 Bad Sectors AND reallocated sector count in SMART is at -0- "?

As for DLG - It’s SMART test is useless since it hides raw value for attribute(i accidentally marked C7 attribute instead C6 in DLG window on screen shot) .