Yes, Long Test is what you want. Does it complete with no errors?
If the drive has any errors I would replace it. If it's within a year of purchase you can contact Seagate Support for replacement under warranty. Show them the screenshot of the Long test which uses their tool (the best).
Then do this gold standard Clean Install that compiles the best possible Install of Windows which will stay that way as long as you stick with the tools and methods given, has zero reported problems, and is better than any amount of money could buy: http://answers.microsoft.com/en-us/windows/wiki....
If it has no errors then I'd still do the gold standard Clean Install after wiping the drive with Clean Command from the Command Prompt in the booted installation media I show you how to create in the tutorial above. Press Shift + F10 at first screen, or at second screen choose Repair Your Computer > Advanced Troubleshooting > Command Prompt:
https://www.tenforums.com/tutorials/85819-erase...
You will get and keep the best possible install to the exact extent you stick with the steps, tools and methods in the linked tutorial. It's a great learning experience that will make you the master of your PC because you will learn everything that works best and how to apply it with your own hands.
Keep me posted on your progress as I will be here to help until the case is resolved.
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Linked tutorial is from a trusted Microsoft MVP