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Windows 7: Cannot install win 8.1 x64, on MBR HDD running Win 7 on UEFI

16 Oct 2014   #1

Windows 7 Ultimate SP1 x64
Cannot install win 8.1 x64, on MBR HDD running Win 7 on UEFI

I currently have a Custom built computer, based on gigabyte GA-990XA-UD3 mobo.
I have a Segate Barracuda 1TB HDD that is currently in MBR format, and is full of data.
The mobo uses UEFI.
Now, I have read that uefi REQUIRES us to use a GPT HDD to boot up Widows 7/8/8.1. But my HDD, in MBR runs win 7 x64 perfectly. Now, I am trying to install win 8.1, but the setup says that it cannot be done because the HDD is in MBR. Now, I have lots of data on the drive and do not want to format it, delete all partions, convert to GPT, and then insatall 8.1. Any Help?

My System SpecsSystem Spec
16 Oct 2014   #2


You should have a BIOS setting for CSM, Compatibility, or Legacy BIOS to enable so that you can use an MBR disk for booting OS and/or data. If you're unsure post back the settings choices for these. Pictures will help. Screenshots and Files - Upload and Post in Seven Forums

Then be sure to boot the installation media as a legacy and not UEFI device, from the BIOS boot menu or Boot Priority order.

If you want to try to adapt the OS on the HD to run on the new hardware you can try to Make Windows 7 bootable after motherboard swap

In either case it may require confirming the Partition Marked Active is the 100mb System Reserved (preferred if you have it) or C, then running Startup Repair - Run 3 Separate Times to get it started.

Otherwise you can reinstall to the OS partition if you have your data separated to another partition. But it's always risky to not have data backed up. You can back up 15gb for each Windows Live ID to the cloud with MS OneDrive. Here is also a way to
My System SpecsSystem Spec
17 Oct 2014   #3

Windows 7 Ultimate SP1 x64

First of all, thank you very much for helping me out.
I found the"legacy" BIOS setting in the 'features' section of my BIOS, and after reformatting the USB drive to NTFS, was able to install Windows 8.1 successfully.
I already have all my data backed up to an external HDD, but I did not want the hassle of restoring all that amounts of data back.
Anyway, thanks, I appreciate your help very much.
My System SpecsSystem Spec

17 Oct 2014   #4


Nice work! Glad to help.
My System SpecsSystem Spec

 Cannot install win 8.1 x64, on MBR HDD running Win 7 on UEFI

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