Disk Management is helpful to find out if Windows identifies the hard drive even if it does not show up in File Explorer. Access it using the keyboard shortcut Windows + X, then choose Disk Management. Identify the particular HDD from the available list. In case the hard disk is listed without the drive letter assigned to it, assigning one should solve the problem. In case it is listed in the RAW, unallocated, or offline mode, be careful while formatting, initializing, or creating a partition of that particular drive, especially if there are any important files on it. In case the physical hard drive does not even get detected by Windows, check the connection cable and power supply and then test the HDD on a different PC.