Lleva una particion HPA (Host protected area) y no podras con programas normales deshacer o modificar esa particion.
Usar el programa HDAT 2 es con el unico que podras.
Debes de tener bastante idea para gastarlo y no joder el usb.
El programa esta en una iso que arranca en antiguo MSDOS.
Un saludo y ya comentas si te aclaras.
PD: he encontrado esta mini guia:
DUMMIES' GUIDE TO REMOVING HPA WITH HDAT2 TOOL
1) Backup all the data to somewhere else unless you plan to have unRaid rebuild the data after removing HPA.
2) Download HDAT2 CD Boot image:
http://www.hdat2.com/ Filename: HDAT2ISO_48.RAR
3) Burn the disc and boot it up.
4) Upon booting the disc, select option 1
5) Type HDAT2 and hit enter
6) All your drives will be shown in HDAT2 console. Drive with HPA partition will be labeled "HPA_IS_ACTIVE".
7) Hit ENTER on the drive you wish to remove HPA
8) Select "SET MAX (HPA) Menu"
9) Select "Set Max Address"
10) Next screen will show how much space the HPA partition has taken (Current Hidden). New hidden is automatically set to 0. Simply hit "S" and HPA partition will be wiped out.
11) Hit any key and it should bring you back to the main menu. If not, hit escape until you see the main menu. Verify that HPA partition is indeed removed. Reboot and pop the disk back to unRaid.