I have a 3Tb WD My Book Essentials USB hard drive which is suddenly not being recognised by Windows Explorer in Windows 8. It does show up in Disk Management as Disk 1 but doesn't have a drive letter assigned. All options include add a drive letter are greyed out. Only the properties of the drive can be selected. When I try to select the drive, Windows 8 tells me that I must initialise the disk. I have over 2 Tb of data on that drive I don't want to lose and can't back up. Have removed it from its case and put the drive into a usb dock but it still isn't getting recognise by the system. Can anyone help please?