I recently purchased a Western Digital Black 4TB hard drive to work alongside my 1TB boot drive. After installing it, Windows booted perfectly fine, but the new drive was barely recognized by Windows (I'm using Windows 10) http://imgur.com/vj03rA7 After attempting to initialize it, I got an error saying "The request could not be performed because a device error". I later figured out that this was because I was attempting to format it as MBR, but since the drive is over 2.5 TB, I tried initializing it as a GPT. I later got an error saying the drive was not the minimum required capacity to be converted to GPT. My guess is that it's because the hard drive's capacity isn't recognized by Windows, so it reads it as 0 GB. I tried things such as going into a command prompt and converting it from there manually, installing new motherboard drivers, and purchasing a new SATA III cable because I thought my current one was potentially faulty. None of these solutions worked. I was also told that my motherboard could potentially not support 5TB of total storage, but I doubt this is the case. My motherboard is a fairly high-end MSI Krait Z170, so that combined with the new drivers made me assume that my issue is not caused by the motherboard. I also installed Hard Drive Sentinel to see if it would pick up anything more. The drive was detected, but no other information was read. I also attempted to reinstall the hard drive's drivers, but I was still met with the same issue. Occasionally, the hard drive is no longer detected, but then comes up after refreshing Disk Management or rebooting my PC. The BIOS also occasionally won't detect the second drive. In the end, this new drive just doesn't want to be picked up by Windows possibly for the issues listed, but I'm rather confident I'll find an answer asking here. Thanks to everyone!