Most people don't realize that the drive manufacturers (WD, Seagate, etc.) just assemble a bunch of parts that were made by other subcontractors and the bulk of troublesome drives, these days, are due to an issue with one of those parts. If a given model has a high failure rate, which part is substandard becomes known and can usually be found at sites like HDDGURU and/or a search for that model number gets numerous hits from data recovery firms.
Regardless, the fact that HDTune reports a bad sector does not bode well for the health of that hard disk drive and, especially in light of the fact that these things tend to deteriorate rather rapidly once they have begun to fail, I would be cloning it to a different drive before it got worse.
If (!!!) you have everything backed up and you are prepared for it getting worse, go ahead and leave it; but, be warned that it may fail completely as I write this or it may be several more months before that happens.
And not let's forget how Newegg & others packaged OEM HDD's until a couple of years back, now WD ships these to resellers in secure fitting boxes with end caps on each end of HDD to prevent damage This was my first ever WD RE4, purchased new on the Newegg site, the warranty expired just months back. Came to me in a dented box & drive was wrapped in brown paper with foam peanuts on top.
So figure end part of this on the reseller and delivery service end also, I know to be fact that if small packages 'falls' from a pallet in UPS hubs, some employees kicks these around, totally ignoring the glass symbol on these. May explain why the dent was on side of box. FedEx, who Newegg uses more these days, are more careful with package handling.
I presume due to the high RMA rates of these drives, prompted WD to package these better, even if sold as OEM or 'bare' drive. Have some still quite good 1TB Samsung HD103SJ HDD's that were reverted to backup usage, these were properly packaged in a plastic container before I knew of the RE4, got one from both Newegg & Amazon. The latter one was on it's way when the infamous 'drive shortage' that never was caused HDD pricing to double & then triple took place. By the time it was halfway here, the $49.99 HDD was $99.99, had to double check to prevent what I thought to be an overcharge or typo. That action would end up imploding in the HDD OEM's faces, as that's when the SSD industry came together with a price war, many turned to these, the rest is history. Corporations are not exempt from reaping what they sow.
A true shortage, as were many items during the Great Depression & both World Wars, are when folks had to stand in line for days to get what's available. Instead, one could still get these in the same amount of time, only at a jacked up price. This also helped many eBayers sell their used models fast with only a modest price increase.
As far as my data goes, backup quite often to protect against not only drive failures, also Malware/Ransomware protection (as denoted in my sig), with items of high importance on more than one drive, so could survive a drive failure. A quote from the link which Havachat posted above.
Ideally with the cost of storage now, just replacing and using a new drive seems ideal to me.
That's how I feel about it, and don't cheap out with drive replacement, was purchasing WD RE4's, now it's their Gold models instead, with SATA-3 & minimum 128MB cache. Some models has 256MB cache and may be helium filled, have two of the 2TB models in usage now. Storage is another area of we get what we pay for, be it HDD or SSD. Many, to include members of my family, have asked me, 'why the stockpiling of drives?', Would always reply with the same response, 'I never know when these are needed'.
As long as things doesn't get worse, will leave the drive as is, or may swap into a less used PC with exact model/size of drive, have at least four of this size, and three of the 1TB capacity. It was simply the first time I've seen a single sector become bad, unlike SSD's, these aren't shifted to a reserve area where unseen & being on the top row concerned me.
Thanks for all of the responses received, I believe the issue to be resolved for my comfort zone.
BTW, here's the link for the DiskFresh tool, on down the page a bit, also provided below. Free for Home users. Some prefers this over the crappy patch that Samsung released for the 840 EVO lineup of SSD's. This didn't affect my 120GB model, although did the 250GB one badly, the one in this machine. So when read speeds diminishes, will try running DiskFresh first. Yet it doesn't repair bad sectors no more than the Samsung read restoration utility 'fixes' the 840 EVO read issue, it's just that some owners are reporting a better experience with this tool instead of what Samsung provided. Some also says that it prevents 'software rot', an issue brought to my attention by Leo Notenboom, founder of the 'Ask Leo' site, the fast formatting style of today would seem to compound the issue. Only most of us doesn't hang onto the same Windows or other OS install for 5+ years anymore before reinstall or moving to another OS.
Download DiskFresh For Home Users