1) A Spin retry event is logged each time the drive was unable to spin its platters up to the rated rotation speed in the due time. Spin-up attempt was aborted and retried. Theoretically, it may indicate a problem in the hdd mechanical system but can also be caused by a loose power connector.
2) I see from your picture that the hdd had 2 spin retries. Thats not a big deal. HDD aren't perfect devices and are designed to recover from ocassional errors. A momentary power loss or case movement may have caused it.
3) Hdtune is not 100% reliable. Download and run the manufacturer's diagnostics, you can even try Speedfan, that'll give you a better idea.
4) Check your cable connections. Also, always keep critical data backed up. Also, best to make a system image of the C: drive (windows partition) from which you can restore, using a tool like Macrium Reflect. These things should be done irrespective of what HDtune says.