I Recently purchased and installed Windows 8.1 Pro and installed it, Before installing it I had two HDD's installed, The one that came with it; Samsung HM321HI, and a secondary one; Samsung SP2504C. I then installed Windows 8.1 Pro and after installation the secondary HDD Is not appearing in the "My Computer" window. I have also tried using the "Device Manager" and the "Disk Management" tools. Device manager shows the two HDD's as working perfectly fine, Disk Management shows the first one fine but the second one needs "Initializing" which I try but shows an error of "Incorrect Function". Since my old laptop was never going to be used again due to it's mother board being fried, I took the HDD from that and connected it to my PC, which works fine. One question it leads to is "why is my computer not initializing my secondary HDD properly when it was working perfectly fine before I went from Windows 7 Professional to Windows 8.1 Pro?".