USB memory stick presents as two storage devices
Some USB sticks can be configured to present themselves as two or three storage devices. This works at firmware level – instead of a single disk with partitions, the OS sees two or three separate devices, so you cannot just repartition it.
(U3 is just one example. Another manufacturer, the name of which I forget, sells USB sticks with a ~200 MB read-only partition holding ~20 MB of promo JPEGs and Kaspersky trialware.)
You need special software to reconfigure the drive. Unfortunately, most such programs are Windows-only, not officially available to the public, and you have to know the flash controller being used inside your USB stick and find the specific program.
- Tools for U3 drives are widely available.
- UT165 – I have used this myself to remove the aforementioned Kaspersky junkware, seems like a common controller type.
- iCreate
if anyone has programs for other types, feel free to add.
I have already seen several devices of this kind, and I have been unable to modify the partitions in order to end up having just an ordinary storage device.
I'm afraid that the manufacturer makes these configurations at hardware / firmware level and these can not be undone, at least in a ordinary way.