There are two ways to start this function on partition magic:
1) Click on "Disk" in the top menu, click "Delete All Partitions" from the drop down menu.
2) Click "Delete All Partition" under Disk Operations in the Action Panel.
Delete All Partitions will delete all the partitions in the present chosen disks.
Note: May cause Windows to not start properly when used on partitions containing the boot partition or system partition.