Could you get the SMART status, as requested by fzabkar ?
If there's any suspicion of a physical issue, and no backup, running CHKDSK is a (very) bad idea. Scanning a defective drive with data recovery softwares is also a bad idea, because you don't actually recover anything during the scan, whatever is read is going to have to be read again (if at all possible) at the extraction stage, at which point the condition might have further degraded, meaning that the data which was barely read earlier can no longer be actually recovered.
If you are (very) lucky, it may still be possible to clone or image the whole drive, with only a few defective spots, using ddrescue or HDDSuperClone (and then scan the clone or image with a recovery software, or several – once the data is stored on a healthy drive various attempts can be made to retrieve as many valid files as possible), but if indeed there's a head issue, you're in for a lot of trouble (especially if the 4TB HDD is nearly full – as
this can happen), and even that method (which is on the low end of the data recovery skills spectrum) requires a good deal of in-depth understanding of the intricacies of HDD operation. Arguably if you did what you did you don't have it, therefore the advice of handing it out to a data recovery professional is a wise one – and it could be cheaper to do this now rather than messing with the drive further and having then to pay a premium to get it done by a pro anyway once it becomes clear that there's no other option, and getting an inferior recovery rate in the end.
@Dananjaya
What makes you think that there is definitely a head issue ? The clicking sounds ? Couldn't these be calibration noises ? What would a pattern like “one click every 30 seconds” correspond to,
technically ?