How to partition a Windows drive that was previously formatted in Mac?
Mac OSX may create an extra 200 MB EFI partitions at the start of a drive hence you may see this EFI partition in Windows. The Windows Disk Management tool can’t delete these EFI partitions, and you’ll see the “Delete Volume” option grayed out. This article describes how you can clean these partitions in DOS command mode and re-format your CalDigit drive.