I felt I must warn you to proceed with caution.
I just opened mine under linux using fdisk and tried to list the partition table. See what fdisk reported below. Now this is similar to what the preformatted usb drives had - only plainly even linux doesn't really understand it. While in may be possible to delete the partitions, it's obvious that the PP is meant to be set up like this. Maybe yours is now different due to something the Apple system has done and hence the problem.
Code:
# fdisk /dev/sdc
Command (m for help): m
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (experts only)
Command (m for help): p
Disk /dev/sdc: 385 MB, 385875968 bytes
12 heads, 62 sectors/track, 1012 cylinders
Units = cylinders of 744 * 512 = 380928 bytes
Disk identifier: 0x69737369
This doesn't look like a partition table
Probably you selected the wrong device.
Device Boot Start End Blocks Id System
/dev/sdc1 ? 2513134 2739867 84344761 69 Unknown
Partition 1 has different physical/logical beginnings (non-Linux?):
phys=(68, 13, 10) logical=(2513133, 6, 42)
Partition 1 has different physical/logical endings:
phys=(288, 115, 43) logical=(2739866, 9, 25)
Partition 1 does not end on cylinder boundary.
/dev/sdc2 ? 2286989 4800271 934940732+ 73 Unknown
Partition 2 has different physical/logical beginnings (non-Linux?):
phys=(371, 114, 37) logical=(2286988, 6, 38)
Partition 2 has different physical/logical endings:
phys=(366, 32, 33) logical=(4800270, 1, 4)
Partition 2 does not end on cylinder boundary.
/dev/sdc3 ? 4 4 0 74 Unknown
Partition 3 has different physical/logical beginnings (non-Linux?):
phys=(371, 114, 37) logical=(3, 5, 32)
Partition 3 has different physical/logical endings:
phys=(372, 97, 50) logical=(3, 5, 31)
Partition 3 does not end on cylinder boundary.
/dev/sdc4 1 4617088 1717556736 0 Empty
Partition 4 has different physical/logical beginnings (non-Linux?):
phys=(0, 0, 0) logical=(0, 0, 1)
Partition 4 has different physical/logical endings:
phys=(0, 0, 0) logical=(4617087, 11, 62)
Partition 4 does not end on cylinder boundary.
Partition table entries are not in disk order
Command (m for help):