I ran the test later but without checking the box "Scan for and attempt recovery of bad sectors" it gave no errors were found.
Something strange also happened, when I compared the SMART results before the first test and after, I found the values of the "raw read error rate" changed, here are the details: http://postimage.org/image/n61a9xal3/
Also the used space on the drive changed slightly (increased) after the test, though the size of all the data inside did not.
The initial normalised attribute values of 253 obviously reflect the initial state of a virgin drive. It is only after the drive has begun seeking and reading and writing that enough statistical data are accumulated in order for these attribute values to become meaningful. In short, there is nothing wrong.
As for the CHKDSK error, it appears that there was an inconsistency between the drive's actual free space and the map of free clusters in the $BITMAP metafile. NTFS relies on the information in the $BITMAP to allocate disc space to new files, and it also updates the $BITMAP after deleting files.
As usual a very well informed answer. Thanks fzabkar...
Well what about the changing in used space values? Each time I run the test the value of the used space increases some 4kb - 8kb. Specially when running the CHKDSK, when I ran the WD drive utilities', and the WD data life guard's extended tests nothing changes, only the SMART values keep shifting from 200 to 253 and vice versa, but not the used space.
Another thing, Is it normal to see the LED light of the hard drive from the opening in the top right of the casing?