I would recommend running a Full Hard Drive Test to confirm the issue, but it does sound like the drive may be beginning to fail. Even if your hard drive wasn't failing, I would highly recommend backing up your important files so that you are better protected from data loss in the event of any possible failures.
If your computer is within warranty, it should be a quick process to contact Dell for a replacement and inform them that the hard drive failed when you ran PC-Doctor diagnostics.
Please let me know if you have any questions or additional issues.
Thank you,
Kris