I have bought a second 1TB WD 2.5" My Passport Essential USB3.0
When connected to my laptop Win 7, File Explorer does not show any new drive.
When clicking into Computer Management → Storage → Disk Management:
It appears as Disk 2 but no drive letter can be assigned.
There is a remark saying that “The disk is Offline because it has signature collision with another drive that is online”
Another disk here means Disk 1, the existing WD external drive which is the same model as Disk 2.
Any one has idea on how to fix it?