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I used AOMEI Partition Assistant Standard Edition 5.6 to convert a MBR disk to GPT and it workd great. Unfortunately the first attem[t I selected the wrong disk, which was already GPT. Aomei let me continue anyway and when I clicked Apply failed (I did not record the error, wish I had) and trashed the disk, losing all 4 partitions.
I was able to recover them using another partition recovery program so not a big deal, but Aomei should not have let me do what I did. It should have known the disk was already GPT and refused to continue.
This is a change that should be made to a future version of the product.