Laptop drive constantly spinning up

I have WDC WD10SPZX-08Z10 mounted inside my Dell laptop together with an SSD. The SSD is C: and has Windows 8.1 installed. The HDD is D: and is used for storage of videos, photos, and such. When I am browsing through the HDD, it constantly spins down and has to spin up again. For example, when watching a video, the video will pause, the drive will spin up, and then continue. Or browsing a directory of photos, when viewing the next photo, there will be a pause while the drive spins up.

I have all the power saving options turned off. What could be the problem? I understand that the drive might spin down when not in use, but it’s in constant use and it acts like this.