PC not recognizing My Book

Recently  bought  WD My Book Essential 2 TB 1140 and installed it to HP Touchsmart desktop running Win 7 Pro.  Everything was fine for two weeks or so then drive not recognized in My Computer.  Attached the drive to a Dell Inspiron 6400 running XP Pro.  See the drive everywhere but My Computer.  Attached the drive to another Dell running Win 7 Home Premium with same results.  Have tried every remedy on this site and what is directly recommended by WD tech support.  Simple issue…PCs know the drive is attached, but I cannot access drive.  All PCs have USB 2.0 ports.  WD drive is USB 3.0 and compatible with 2.0.  Does anyone have  a solution or should I replace the drive or forget WD and get another vendor?

Quick question: Is the drive connected to a power strip? If so, connect the unit directly to the wall socket. Otherwise you will need to replace the unit.