I was using an HFS+ 3TB Buffalo hard drive on my iMac and plugged it into my laptop running Windows 10 Tech Preview. It didn't show up in Explorer but I think I may have formatted it in Disk Utility. Somewhere along the way, a dialog popped up that mentioned a choice between GUID and something else and I clicked GUID, and now it won't work on the Mac or the PC. Did I format it? It must have worked INCREDIBLY quickly to format 3TB in about 3 seconds....
Also, the partition that used to be there before doesn't show up in anything.
Is there any way to recover the data?
You can't recover it in Windows, you will have to recover it in OSX. Windows rewrote the partition, which means your drive is likely largely still intanct, but you need a utility on the Mac that can recover a lost partition.
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