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So I took some files with me on my external HDD while going on vacation. Through a series of events, I ended up storing the data in a NTFS formatted partition defined in a GUID Partition Table. The only computer I have is a Windows XP home box, which does not have native support for reading GPT's. So far everything I have read online suggests wiping the disk and reformmating to MBR. Is there a way to convert it without wiping out the data or to access the data as is?

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migrated from Jun 3 '11 at 10:29

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Yes, you can convert a bootable GPT disk to a bootable MBR disk without losing its contents if it is not larger than 2TB. I used Aomei Partition Assistant Std Edition.

Do not do this on a drive larger than 2TB. Drives larger than 2TB are supposed to use GPT to be bootable. Drives 2TB or less can use either GPT or MBR; but GPT is not supported for boot disks on older OS like XP (32- or 64-bit) and Win7 (32-bit). Win7/64-bit supports GPT as a bootable drive type.

Also, older disk utilities will not work on GPT drives (and may in fact screw them up) so if you are in an environment with older OS then use MBR whenever possible. Using MBR or GPT does NOT affect disk performance.

Do the following:

  1. Install your GPT drive as a data (non-boot) drive on your XP system, or on a Win7 system (which is what I used).

  2. Download and install Partition Assistant.

  3. Using Partition Assistant, delete the first two (small) partitions (the EFI and the MSR partition) from the GPT drive. Hit "apply" and let it do its thing. When it's done the space previously allocated to the two initial partitions is now a single unallocated region.

  4. Resize the 3rd partition (the one with your data and boot image) to include the unallocated region created in #3 above.. Hit "apply" and let it do it's thing. When it's done your boot partition now spans the entire disk and is the only partition.

  5. On the left side of the disk graphic where it says "disk 2: GPT" or something like that, right click and select "convert to MBR disk". Then right click again and select "rebuild MBR". Make sure to select the MBR type for the OS you wanna boot... Hit "apply" and let it do those two things.

When finished, your disk is now an MBR bootable disk. Shut down, remove the old boot disk, and you should now be able to power up and boot the one you just converted to MBR format.

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The question doesn't mention booting, nor does it mention multiple partitions. But the tool mentioned should probably work nonetheless. – jiggunjer Feb 2 at 5:53

Not free, but this utility might help.

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Before wiping the hdd completely I would give TestDisk a try. It is designed to recover partitions independent of the used partition table. AFAIR is writes the result in form of an MBR partition table.

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