Cctv2240

I recently put in an eight channel Hikvision NVR for a friend. It holds 2 hard drives but he only put in one WD Purple 2TB. Upon turning it on, under hard drive, it lost 0 space used of 0 available. I can't even select it to initiate it or format it. Is there a place in the menu to select which one to use? I figured it would see that only one was hooked up and default to it. Thanks for any advice anyone can give me. It is fully installed so taking it out and apart is a last resort but doable. Thanks