What's up with this 64GB USB thumb drive appearing as two disks?

Here is the explanation directly from Centon:

Question: I recently purchased one of your 64GB DataStick flash drives, and I was surprised to find that the 64GB device was formatted with two partitions. Why is this? Can it be re-configured?

Answer: Due to a limitation in Windows 2000/XP/2003 computers, drive volumes cannot be formatted in capacities larger than 32GB using the FAT32 file system. As a result, to ensure the drive can be recognized by the most number of computer systems, our 64GB drive is partitioned into two 32GB volumes. The Windows formatted capacity is roughly around 30GB.

When the 64GB drive is connected to your Windows computer, it will be assigned two drive letters.

The drive cannot be reconfigured into a single 64GB partion. The partition on these drives is hardcoded into the USB-to-flash controller chip.

So no, your drive is not faulty. They decided that the best thing for you, the consumer, is to actually use two seperate drives. I would be mad if I ordered a USB drive and realized that the manufacturer created this restriction without any mention on the product description page.

It doesn't appear to be two partitions, it appears as two separate drives. If it were two partitions on a single drive, you'd see device names like sdc1 and sdc2.

It's likely the drive is implemented as two physical drives at the hardware layer, and depends on a special driver to allow the OS to see it as a single drive. It may also be a chipset limitation (in whatever chipset is used in the thumbdrive hardware).

Either way, it doesn't seem likely that you'll be able to force it to be seen as a single drive. If you require this functionality, return the device for a refund and buy a different device.