in the sdk, take these files out of the tools folder and place them in the root of your c drive adb.exe and adbwinapi.dll. boot your phone into recovery. plug it in to pc. now, open command prompt and cd to c:\ . like this cd c:\
now type adb shell
you should get a # symbol.
now type or copy paste this
echo /dev/block/mmcblk0 > /sys/devices/platform/usb_mass_storage/lun0/file
give it up to 20 seconds or so for the drive to be available
de facil comprensión.