Hi si239 and Welcome to ROG
Go into your Bios and check to see if indeed the Bios recognizes your HDD. If indeed it is recognized, then configure accordingly in boot drive priority.
If you are able to get into Windows, then run a CHKDSK to be sure all is OK with your drive.
We owe our existence to the scum of the earth, Cyanobacteria
My System Specs:
MB:ASUS ROG Crosshair VII Hero/WiFi GPU:EVGA GTX 1080 sc PSU:Corsair AX-1200i
CPU:AMD R7 2700X Cooler: Corsair Hydro H115i Case: Corsair Carbide 780t
Memory:G.Skill TridentZ F4-3200C14D-16GTZR SSD:Samsung 500GB 960 EVO M.2
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