Use flashed 360 to dump your nand. Steps: plug usb drive in to xbox360 and turn it on. launch xexmenu or fsd and go to usb drive and then "flash 360" folder and run Flash360.xex file. You,ll see three options : Button A: write updflash.bin to nand Button B: write update areas of rebooters Button X: backup current nand to file now becareful press X button from your 360 controller to backup nand and then it will ask for save entire nand then press A button to continue. that will save your nand backup named "flashdmp.bin" file in the root of "flash 360" folder. Flash 360: http://www.mediafire.com/download/eqdzcfbma9znxkn/flash+360.rar
I saw this in chinese website A9vg, but I can not download sonthing. Thank you for I can get help here