I have a Western Digital 2TB external hard drive, model WDBAAU0020HBK-01, that I was using for backup on my PC. I noticed one day that it was not signing on along with my external Seagate drive. When I went to My Computer (I have a Windows 7 PC), only the Seagate was visible. I tried a number of things to get the drive recognized, but ultimately, I discovered that the power supply was dead. So I went to Fry's Electronics and got a universal power supply capable of 1800 milliamps (the original power supply says its output is 1.5A or 1500 milliamps. Plugged in the new supply (after checking the polarity--center is positive) and got nothing. After awhile, Windows installed a driver called Initio, but never recognized the drive as a USB hard drive. In other words, the drive's electronics are apparently dead, too.
The Backblaze cloud backup company issued a report recently noting that of the thousands of hard drives they use, Western Digital drives have the highest failure rate. (Hitachi drives have the lowest.)
I just plugged the drive in one last time and nothing at all was recognized or connected.
Hard dive failure is always a cause of unhappiness, even with another backup and cloud backup.