Computer does not start up when connected to My Book 4TB

When I connect MY Book (4TB) to my computer before turning it on, my computer does not start up.  I only get a black screen.  If I disconnect the My Book and then first start up my computer, I am able to plug in My Book and read all the files, backup, etc.  Why won’t the computer start when My Book is connected???

??? Wrong Forum? This is for “My Book Live” vs “My Book”…

How to tell? Easy, MBL (NAS) does not have USB, MB (USB HD) does…

Check the boot order in the BIOS USB needs to be after main HD,

Joe