Had bought a USB2 external MyBook drive. It expired in 8months, failing SMART tests. WD replaced it under warranty. Bonus: The replacement drive is a USB3 drive.
However, on 3 occaisions in the last 2 months the drive has been recognized by the computer in Device Manager, but does not show up in the Windows list of disk drives. SMART and all other diagnostic tests are OK. Re-formatting solved the problem. Firmware updates made no difference. Drive is out of warranty (same expiration date as the original drive).
Today, I gave up on the drive. The case was pried open. The contents are a small circuit board (which provides the USB3 to SATA interface), and a standard WD 1.5TB SATA drive (WD15EARS, 64MB cache).
The drive will be installed inside my computer as an internal drive. WD Smartware software has been de-installed. Windows backup (or a third-party tool) will be used instead.
WD drives are good - but the software and/or the software on hthe embedded interface card has proven to be more than a little dodgy.