4TB HDD not found in Windows Explorer, but detected in bios and Disk Managements.

[PC_fix]

Mobo; Asus Strix z270i (Mobo is boot in UEFI-based system)
Boot drive: Samsung 850 EVO 250GB M.2-2280 Solid State Drive
HDD: Seagate 4TB ST4000DM000 (two HDD, new<no files inside> and old<lots of sentamental files>)
OS: Windows 10 Home 64bit

I have read and tried this(reference):
http://www.tomshardware.com/answers/id-2436443/modify-allocated-space-hdd.html
http://www.tomshardware.co.uk/faq/id-1981330/3tb-hard-drive-work-windows.html
http://www.tomshardware.com/answers/id-3314921/4tb-hdd-recognized-motherboard.html?58d8f099d28f0=reload
http://www.tomshardware.com/answers/id-1696373/4tb-hard-drive-2tb.html
https://www.cnet.com/forums/discussions/internal-large-capacity-hdd-still-not-being-recognized/

In the BIOS and Disk Management the 4TB is detected. But when viewing it in the Windows Explorer there is no HDD 4TB displayed.
The both 4TB HDD is formatted in GTP and NTFS.
Tried plugging it into the other two Sata ports, still negative.
However, putting both in my external enclosure the HDD is detected by my desktop PC.
When using the Disk Mangament in the desktop PC. It shows Unallocated, Right-clicking both the Unallocated and Disk x, the options are greyed out.
I have tried it in my laptop by external enclosure. The HDD is usable there .

What I want is for the HDD to connected directly to my mobo and not by USB to SATA.

My HDD is already GPT and NTFS.
Mobo is UEFI.
Tried switching the 2 4TB in the other 2 sata ports, due to the M.2. Still no change.
Check the BIOS is Up-to-date.
Drivers and chipset is also up-to-date.

If there other solution I might have missed, please comment.
Thanks.

BIOS is up-to-date. I have check for the latest BIOS, the latest update is for Optane.

Device Manager: The 2 4TB is detected.

Disk Managment: Changing the drive letter is not clickable(greyed out).
Please Take note. I did not partition my 2 4TB this way, I partitioned it as a WHOLE.

 

[Emerald]

were they configured in RAID in the external enclosure?

 

[PC_fix]

were they configured in RAID in the external enclosure?

Nope. Using the two 4TB as a separate storage for both external and internal.

 

[XozaShadow]

Does it show in disk management with a drive letter? If not you'll just have to assign one. Is it empty?

You should be able to right click the allocated data on drive overview and select "Change Drive Letter".

 

[USAFRet]

In Disk Management, right click on that drive.
What options does it give you?

 

[PC_fix]

Does it show in disk management with a drive letter? If not you'll just have to assign one. Is it empty?

You should be able to right click the allocated data on drive overview and select "Change Drive Letter".

In Disk Management, right click on that drive.
What options does it give you?

I have also tried to assign a drive letter but the option for doing that is greyed out.

 

[XozaShadow]

Does it show in disk management with a drive letter? If not you'll just have to assign one. Is it empty?

You should be able to right click the allocated data on drive overview and select "Change Drive Letter".

In Disk Management, right click on that drive.
What options does it give you?

I have also tried to assign a drive letter but the option for doing that is greyed out.

It's best to troubleshoot this with a direct Sata connection BTW, not USB.

What does the drive partition show in words, like active or boot?
How many partitions do they have?
How many Sata ports? (make sure your M.2 doesn't take up the sata ports your trying to use.)
Is there data you want to recover on these drives?

 

[PC_fix]

Does it show in disk management with a drive letter? If not you'll just have to assign one. Is it empty?

You should be able to right click the allocated data on drive overview and select "Change Drive Letter".

In Disk Management, right click on that drive.
What options does it give you?

I have also tried to assign a drive letter but the option for doing that is greyed out.

It's best to troubleshoot this with a direct Sata connection BTW, not USB.

What does the drive partition show in words, like active or boot?
How many partitions do they have?
How many Sata ports? (make sure your M.2 doesn't take up the sata ports your trying to use.)
Is there data you want to recover on these drives?

What does the drive partition show in words, like active or boot?
>>> Says it is online for both 2TB.

How many partitions do they have?
>>> I formatted it as whole. But it shows it is partitioned to the 2TB limit.

How many Sata ports? (make sure your M.2 doesn't take up the sata ports your trying to use.)
Is there data you want to recover on these drives?
>>> I have read about this. There are total of 4 sata ports, so I tried switching alternatively between the vacant ports. But still I cannot access the files.

 

[Paperdoc]

Which version of Windows 10 Home are you using? I note that the two units both are Partitioned into 2 TB and then a smaller Unallocated Space. Now, to use ALL of a 4 TB HDD you would have to be using the GPT Partitioning system. BUT the only versions of Windows that come with a device driver for a GPT-Partitioned HDD are the 64-bit versions. No 32-bit version of Windows can use a HDD with GPT Partitioning, no matter what size.

 

[PC_fix]

Which version of Windows 10 Home are you using? I note that the two units both are Partitioned into 2 TB and then a smaller Unallocated Space. Now, to use ALL of a 4 TB HDD you would have to be using the GPT Partitioning system. BUT the only versions of Windows that come with a device driver for a GPT-Partitioned HDD are the 64-bit versions. No 32-bit version of Windows can use a HDD with GPT Partitioning, no matter what size.

The windows is in 64bit. That is also the reason I can use my 32Gb ddr4 memory.
I did not partition it to 2TB. I partitioned it as a whole 4TB. The system made it that way.

 

[Paperdoc]

I found an explanation plus, more importantly, a solution for your trouble, I think. The clue is in the fact that the two 4 TB HDD's each have a block of 2 TB marked as a "GPT Protective Partition". It seems his can be created if the HDD was used in a 32-bit system with certain tools that do not know about GPT systems. It ends up making them inaccessible, and the solution is to wipe each HDD clean using DISKPART, then re-do the Partitioning and Formatting properly using the GPT system.. BUT this will wipe out ALL data on the HDD. Your post indicates, if I read it correctly, that one of these 4 TB units has nothing of use on it, so this would be OK. However, it also indicates that you DO want to preserve files on the other 4 TB unit. Plus, it seems to indicate that the disk containing data can be accessed if it is mounted in an external enclosure.

So, here's what I suggest. Remove the HDD that contains the data you want to preserve, mount it in the enclosure, and make SURE you can see the files you want and access them. Then disconnect this unit and set aside safely. Now, use the cleaning procedure on the 4 TB unit with nothing useful on it and get it re-Partitioned under GPT as one large volume you can access. Reboot, reconnect the external drive, and copy all your data over from it to the "fixed-up" 4 TB unit. VERIFY that you got all your files copied and you can access them. Next, shut down, remove the "fixed-up" unit now containing the copied data, and set it aside for safety. Move the other 4 TB unit back into your desktop machine and clean it also,so you have the second one re-arranged as a GPT unit of 4 TB all usable. Shut down, re-install the first 4 TB unit, and it should all work.

The explanation and cleaning details are in this article from Seagate:

http://knowledge.seagate.com/articles/en_US/FAQ/207837en?language=en_US

which includes a link to further info from Microsoft.

NOTE their highlighted Note and Warning. You MUST keep careful track of which HDD you are working on so you don't destroy data on the wrong drive!