Adding 4tb HDD not working as I hoped

I have a Windows 7 Ultimate (x64) Service Pack 1 (build 7601.24106) on an ASUSTeK Computer INC. M3A78-CM Rev X.0x MoBo.
I just purchased a Seagate Barracuda 4tb drive to install as backup. The Mobo supports 6 Sata drives and this was my 5th drive.
First, I couldn't even boot it up. So I removed the other drives, except the boot and it allowed me to boot. (I seem to recall a 4 Sata limit from somewhere??)
Then when it booted, I entered Disk Management to format the new drive and it automatically segmented the drive into 2 partitions.
Disk Management allowed me to format and activate the first (primary) partition, but I can't do anything with the remain partition. All of the Tasks are greyed out.

Any suggestions for either issue?

Google-> Primary partition limit


You can create a maximum of 4 primarypartitions, or 3 primary partitions and 1 extended partition then add up to 128 logical volumes in that extended partition.

Support.Microsoft.com > Windows support for hard disks that are larger than 2 TB

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Summary

In order for an operating system to fully support storage devices that have capacities that exceed 2 terabytes (2 TB, or 2 trillion bytes), the device must be initialized by using the GUID partition table (GPT) partitioning scheme. This scheme supports addressing of the full range of storage capacity. If the user intends to start the computer from one of these large disks, the system’s base firmware interface must use the Unified Extensible Firmware Interface (UEFI) and not BIOS.

This article outlines Microsoft support across all Windows versions since Windows XP. It also describes the requirements to address the full storage capability of these devices.

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Then when it booted, I entered Disk Management to format the new drive and it automatically segmented the drive into 2 partitions.

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I've never heard of automatic partitioning before. Is this your first 3TB+ drive? That motherboard is fairly old, so I wonder if the BIOS properly supports 3TB+ drives.

Yes, first 3tb+ internal drive. I have a 4tb external/usb drive, but don't remember doing anything different to it.

When I opened Disk Management, it only allowed me to format the first 2tb. Does that make sense? I didn't realize there was a limit if the HDD was formatted to 2 drives.

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When I opened Disk Management, it only allowed me to format the first 2tb. Does that make sense?

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Yes. That sounds like a BIOS compatibility issue with 3TB+ drives. You can try updating to the latest BIOS and see if that helps.

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I didn't realize there was a limit if the HDD was formatted to 2 drives.

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No, that's not the problem. It's a BIOS limit of drives over 2.2TB.
https://www.pcworld.com/article/2350...rd-drives.html
http://knowledge.seagate.com/article...S/FAQ/218619en

Once you get the BIOS updated, use Disk Management to initialize the drive by using a GUID partition table (GPT) partitioning scheme.

If you also want to make boot from the drive, the system’s base firmware interface must use the Unified Extensible Firmware Interface (UEFI) and not BIOS.