Two 4.0TB My Book at the same time ,Widows Only Recognize one at the time!?

HI

I Have a All-In-One Asus Desktop PC and it’s fairly new model so has latest updated software ,“i hope” ,and it has 4 USB3.0 and 2 USB2.0 Ports also has windows 8.1 and as far as i can think  every thing works fine until i bought Two External 4TB My book one for storing Data and one for back up and both of them works fine and windows recognize them as soon as they pluged in but only if they plug them seperately .when i try to use them at the same time windows randomy recognize one of them at the time

if i want to connect the other one and use it i have to unplug the other one First !! which making back up like this very hard for me

I have WD Smartware instaled in it has latest update and when i plug both of them at the same time it says for one of them randomly “no writable partition found” (both work fine and has data stored on them and they both are NTFS)

aslo i have these following External HDDs and they work at all time with no interfirence with each other at the same time

1-WD My BooK 3.0 TB (always pluged in)

2-WD Elements 2.5 TB (always pluged in)

3-Seagate Plus 3.0 TB (always pluged in)

4-WD My Book 1.0TB (eccationaly pluged in but works fine)

5-WD My Book Elite 1.0TB (eccationaly pluged in but works fine)

6-WD My Passport 500GB (eccationaly pluged in but works fine)

i have tried all USB 3.0 and USB 2.0 Ports even pluged one Into USB 2.0 and the other one to USB3.0 at same time 

but same result and looked in the Device manager didn’t see any errors

also installed “RENESAS-USB3-Host-Driver-30230-setup” and USB3.0_allOS_2.1.28.1_PV from intell website

but the software won’t work ,the error message says “USB 3.0 Host Controller Not Found”

when click on HDDs Propertie it says for botn of them " WD My Book 1230 USB Divice"

can some one please help me?

sorry i found the solution .it was disk colision something like that 

for those who may have the same problem you must go to my computer → disk managment ->fhttps://wdc.custhelp.com/app/answers/detail/a_id/6571

follow the instraction on page above