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I'm forced to change my motherboard. I just purchased a new ASUS Sabertooth 990FX. I read that it's UEFI based. As far as I know, UEFI motherboards support GPT disks. My current hard drive is MBR.

Can I simply plug it into the new motherboard and be able to boot Windows?

Or do I have to perform some kind of conversion steps before/after replacing motherboard?

Clearing partitions is totally out of the question. Formatting just the boot partition is undesirable but feasible if really, really needed.

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Of course I already know that I'll get licensing troubles with Win7 when changing motherboard – usr-local-ΕΨΗΕΛΩΝ Nov 1 '12 at 19:52
UEFI can (and should) support both GPT and MBR. – Hennes Nov 1 '12 at 19:53
up vote 1 down vote accepted

I went from a Gigabyte 880 (non UEFI) to the 990FX no problem. The issue you may hit would be the controller mode (AHCI/Legacy -- which is unrelated to the partitioning really). I think the 990fx defaults to legacy, but I don't recall. I also have MBR discs.

It worked fine for me, that being said - I am a believer in fresh installs with major hardware changes, so I only ran that around a week or so and may have not hit any odd issues that are, imo, unlikely.

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Thanks. I already need AHCI and I'm aware of the AHCI boot problem – usr-local-ΕΨΗΕΛΩΝ Nov 1 '12 at 20:05
990 defaults to AHCI for some reasons. Just a pit stop on safe mode to detect all devices and it plainly works – usr-local-ΕΨΗΕΛΩΝ Nov 2 '12 at 22:02
@djechelon That's fantastic to hear, I love my 990FX. Best of luck! – nerdwaller Nov 2 '12 at 22:06

It is possible to convert a MBR disk to GPT using gdisk from any Linux live media. But for booting the disk in UEFI mode, it's not enough – you'll need to create an "EFI system partition" and install an UEFI-compatible bootloader into it. (In Windows, the install CD's rescue mode might work, but I don't know more about it.)

Most UEFI implementations these days have a "BIOS compatibility" or "legacy boot" mode, in which, if no UEFI boot entries are configured, the firmware will try starting the BIOS boot sector instead, and the system will behave exactly as if it was running under BIOS. In other words, your old Windows installation should still work.

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