Not Initialized Disk is a storage device recognized by Windows but cannot be accessed due to absence or corruption of the disk info or the partition table. The problem may be associated with both internal hard drives, SSDs and external drives because of connectivity issues, problems with the file system and hardware malfunctions. At first, you need to inspect the USB cable, port and the power source if you use external drive. You also can use Disk Management for checking the state and size of the disk. If the disk already has files on it, don't click "Initialize Disk" or format the disk, since this will complicate the process of data restoration.