C:\android-tools>fastboot erase hboot
erasing 'hboot'...
FAILED (remote: partition is not allowed to be erased!)
finished. total time: 0.015s

C:\android-tools>fastboot flash hboot hboot.img
sending 'hboot' (1024 KB)...
OKAY [  0.181s]
writing 'hboot'...
(bootloader) image update is bypassed!
OKAY [  0.030s]
finished. total time: 0.211s

C:\android-tools>fastboot reboot bootloader