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in BIOS , UEFI Boot is enabled , ACHI Mode is selected , and the 3TB Hard disk (Seagate ST30000DM001) is installed at SATA Port 3.

However, in Windows 7 64-bit, 3TB hard disk is displayed as 746GB, no matter how do I format or set the settings. I use GPT as partition table ( as suggested by Windows , > 2TB should use GPT ).

How can I get back the full 3TB storage ?

p.s. Motherboard is Intel DH55HC and Intel Rapid Storage Technology software shows the disk capacity is 2.862GB .

p.s. Operating System is Windows 7 Ultimate , 64-bit

UPDATE Somebody marked this question as a duplicate of similar issue with USB closure. But this question is about hard disk directly attached to motherboard via SATA cable.

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This problem is resolved in my 10 years old HP desktop (4 cores), with drive: 3TB Western Digital Green, but it should be the same with Seagate too.

In a nutshell you need 2 things to do:

  • to install the Intel RAID driver (free).
  • to use a good tool for extending the partition to the maximum size, like AOMEI Partition Assistant (freeware).


PS1: After all is setup property, you can uninstall both tools mentioned above.

PS2: If you have any conflict between the new 2TB or 3TB disk and the old DVD-ROM then disconnect the DVD, and get an external one (my case).

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up vote 2 down vote accepted

At last, I found that I have to install Seagate DiskWizard to enable the full 3TB disk space.

Note: The software will erase all the contents of the 768GB.

Download link of Seagate DiskWizard :

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That should not be necessary unless you still somehow use an MBR or have an old BIOS. Did you try to boot from the windows DVD (in EUFI mode) and then diskpart clean from a command prompt (via shift-F10) ? – Hennes Jun 16 '13 at 16:13
Chances are you had a driver that used 32-bit pointers somewhere, and installing DiskWizard replaced that buggy driver. This is a common problem on Windows, although it's more common on 32-bit versions of Windows than on 64-bit versions. – Rod Smith Jun 17 '13 at 16:22

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