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Historically, flash drives have been configured as removable disks and Windows Explorer displays them as 'Removable Media'. Windows 8 Certification requires flash drive manufacturers to configure flash drives as fixed disks. Flash drives configured as fixed disk will show up in Windows Explorer as 'Hard Disk Drives'. Flash drives configured as fixed disks still function the same as those configured as removable disks.
You can still connect and disconnect the flash drives from the USB port without having to power off the computer. You can also still use the 'Safely Remove Hardware' feature when disconnecting.