I installed the following update and the drive stopped working. The drive is My Book Essential 1TB. Microsoft - Other hardware - Microsoft Hardware USB Mouse Installation date: 2/27 2:11 AM Installation status: Successful Update type: Optional Microsoft Other hardware software update released in December, 2010 More information: http://winqual.microsoft.com/support/?driverid=20403529 Help and Support: http://support.microsoft.com/select/?target=hub
Shutdown your PC and remove AC cable (from PC) and USB drive. Wait for two minutes. Reboot and wait until Windows loading completes. Reconnect back your USB drive.
If still not working, uninstall USB drive driver from Device Manager and do the same.