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Windows 7: 3 TB drive can not be converted to GPT

25 Dec 2012   #1

Win 7 Ultimate
3 TB drive can not be converted to GPT

Hi -

My c: drive is an SSD (120 GB) and the e: drive is a 3 TB internal hard drive that appears as 2 TB in Disk Manager.

I believe this is because there is a 100 MB partition on the e: drive titled "System Reserved" that is a System, Active, Primary Partition. The other partitions (2 TB and 746 GB) are unallocated currently.

When I installed Win 7 Ultimate, I didn't ask for any system info to be put on the e: drive. Can I simply format the e: drive and then convert it to GPT?


My System SpecsSystem Spec
26 Dec 2012   #2


Had you formatted the 3tb before in this machine? If not check for a BIOS update to enable drives that large.

Try wiping HD first with Diskpart Clean Command followed by Convert GPT command, then format in DIsk Mgmt.
My System SpecsSystem Spec
26 Dec 2012   #3

Win 7 Ultimate
Yes, it has UEFI

Gerg -

The MSI Z77 series mother board that I have supports UEFI and in the BIOS the "UEFI Shell" is enabled.

Since Disk Manager reports 3 TB, I suppose the BIOS is allowing drives bigger than 2 TB.

If I wipe the HD, that will wipe out the System partition. Does that matter? Is anything really there since I installed Windows onto the c: drive?

My System SpecsSystem Spec

26 Dec 2012   #4

Windows 7 Professional x64 Service Pack 1

Post a fully expanded shot of disk management.

Did you ever have windows installed on the 3 TB drive ? Did you have it connected when you installed windows to the ssd ?
My System SpecsSystem Spec
26 Dec 2012   #5

Microsoft Community Contributor Award Recipient


Did you install Windows 7 x64 in uEFI mode?

Can you post a screen shot of Disk management?

Screenshots and Files - Upload and Post in Seven Forums
My System SpecsSystem Spec
26 Dec 2012   #6


Thanks for the additional information.

Please post back a screenshot of your maximized Disk Management drive map and listings:

1. Type Disk Management in Start Search box.
2. Open Disk Mgmt. window and maximize it.
3. Type Snipping Tool in Start Search box.
4. Open Snipping Tool, choose Rectangular Snip, click New, draw a box around full drive map and all listings.
5, Save Snip, attach using paper clip in Reply Box.

Tell us what is on each partition.
My System SpecsSystem Spec
26 Dec 2012   #7

Win 7 Ultimate

Greg -

I've attached a Disk Management screen capture. There's nothing in the 2047 and 746 GB partitions on the e: drive. Since parrt of my question is "what's in the 100 MB Sys partition?" I don't have an answer for you.

To answer other questions, the 3 TB drive is new and has never had Windows or anything else on it. When I installed Win 7 Ultimate 64 bit, I don't believe there was any option for enabling / disdabling UEFI. Since Disk Management says the drive is 3 TB, can't we assume UEFI is working?


Attached Thumbnails
3 TB drive can not be converted to GPT-disk-manager.jpg  
My System SpecsSystem Spec
26 Dec 2012   #8


You may have an EFI mobo but WIn7 is not installed in EFI mode since there are no EFI boot partitions involved. This is fine, actually less trouble. You would have had a much more complicated job installing to UEFI (Unified Extensible Firmware Interface) - Install Windows 7 with - Windows 7 Forums

Your System boot files are booting C from the larger HD, probably because you never deleted the System Reserved partition, kept that HD plugged in to a preceding drive slot during install, so that the installer wrote the boot files to the first Active partition. We see this a lot.

To resolve it, Mark C Partition Active, power down to unplug the data cable from Disk0, swap the cable to Win7 HD so that it becomes Disk0, set first to boot in BIOS.

Now boot into Win7 DVD or System Repair Disk to run Startup Repair - Run up to 3 Separate Times to write the System boot files correctly to C until it becomes marked System Active.

Now you can plug back in the other HD, wipe it with Diskpart Clean Command, format in Disk Mgmt.
My System SpecsSystem Spec

 3 TB drive can not be converted to GPT

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