Yes, this is what I meant. Thanks. So it's just the pending sectors. It's a Seagate drive, isn't it? They tend to "collect" bad sectors over time. I recommend to closely watch the SMART values and if they increase, I'd replace the drive. You can check the serial number on the manufacturer's web site to see if it's still covered by warranty - if it is, I'd file an RMA before the warranty expires.
Unfortunately, I can't rule out any hardware component in regards to the crashes. It could be the HDD, the PSU or high temperatures, the GPU, or even a software issue (mainly driver). Or it could be as simple as a bad connection of any plug to the mainboard or other component - keep in mind that metals expand when they're getting warmer and contract when they're getting colder.
Here's what I would do: Try to figure out when exactly the crashes occur by putting different kinds of load on the system. I'd start with Prime95 (CPU load) and FurMark (GPU load). If it crashes with either of them, it's either a GPU, CPU or memory issue, depending on the test.
If it doesn't crash, I'd (temporarily) swap the components one by one, starting with the PSU. It's a little bit of work to swap it, especially when there are a lot of cables to route, but IMO it's easier to swap than an HDD. And that could also rule out bad connections, from the PSU cables at least.