1. You need your NAND and CPU Key ( make a Backup from Savegames or other things you may need)
2. Download xeBuild GUI 2.09 and DashLaunch 3.07
3. Make a Freeboot image with xeBuild with your responsive Settings (watch on youtube) if you dont know how
4. Rename it to updflash.bin to use inbuild Rawflash in XELL Menu or rename to nandflash.bin to flash with xenpn.elf (Raw Flash 4) put it on USB (root)
5. Start xbox by pressing the dvd tray you will have a XELL Reloaded let USB pluged in xbox FRONT USB PORTS
6. after Image flashed successfuly , shutdown xbox and plug out the power cord and let it without power for 30 sec put it back (dont start xbox)
7. Take your USB and copy the DashLaunch 3.07 Installer = Default.xex on your USB ROOT
8. Put USB in xBox USB Port and than fire up your xbox
9. now xbox is in Dashlaunch menu press on install (DONE YOu Have DashLaunch Installed) just need to configure for yourself
10. Download latest SystemUpdate from Mycrosoft and unpack it on Desktop rename the $ystemupdate > $$ystemupdate
11. Copy the $$ystemupdate to USB and reset xbox now you will get a promp that there are new updates ,press Yes to install update
12. When Done you can if you need a fresh fsd install reformat your hdd in xbox or just delete fsd folder
13. congrats your on 12.0.16203
Hope its OK and it helps