When I have My Book Essential external hard drive connected to my Dell Studio MT435 (Win 7 / 64 bit) the computer will not boot up on the first attempt. It will freeze at the Dell logo screen. I have to power off the computer and restart it. This is a very consistent behavior.
When I disconnect My Book Essential from my computer by disconnecting the USB, the computer will boot on the first try every time. I have checked to see if my drivers are current via the Windows dignostics, and it indicates that I am using the most current drivers.