HDD swap on CCTV DVR

Hi guys, Can anyone please advise if I can use an ordinary Sata HDD in my CCTV setup. I want to replace a 1 terabyte Sata HDD (current installed original HDD, image attached) to a 500GB HDD. If I can, are there any special considerations I must observe? The make is a flourean.
[Attachment 45876 - Click to enlarge] sorry if image not crystal clear can reimage , cheers.
[Attachment 45877 - Click to enlarge]

Attached Thumbnails