I do not really understand … !!!
I can not use My 2 Passbook 4TB at the same time.
I use Windows 7 Pro.,.
Sorry, my English is not good.
Thanks for all the answers.
Welcome to the WD Community.
Sound like one of the drive is going offline when you connect the second one.
Check on the disk management and change the status of the drive back to online and both drives should show up.
Thank you for your advice
I received instructions directly from WD Official and it can fix my problem.
http://websupport.wdc.com/newSupport/KnowledgeBase/answer.aspx?ID=1284#win
By the setting in Computer Management, and Change Drive Letter …
