first of all, fat white XBox360 of 1~2 years age is moddable, easily.
secondary, there're many ways for 360-mods:
for backup (DVD-DL) play, u've LT+3.
for backup (usbHard Disk) play, u've XKey, Wasabi, RGH.
plus, dual NAND or Trident NAND flash system.
ok for u to google the key words.
read and understand each of those mods before selecting the right one for ur application.