How to install Avatar & Kinect update to Xbox 360 RGH

1. Download the latest update files from the Microsoft website:
http://www.xbox.com/system-update-usb
The downloaded ZIP archive filename will be "SystemUpdate_XXXXX_USB", where X is the dashboard version.

IMPORTANT NOTE: make sure you have the correct dashboard version installed on your Xbox 360 by pressing  XBOX  > "Settings" tab > "System Settings" (select "Yes" if asked "Are you sure you want to exit?") > "Console Settings" > "System Info"
Dashboard: 2.0.XXXXX.0
X must match here and in the downloaded ZIP filename. If it is lower, you must update your kernel first! Tutorial here:
http://csenger41.blogspot.hu/2016/03/how-to-update-xbox-360-rgh-kernel.html

2. Format a USB stick to FAT32 (tool for formatting here: http://www.mediafire.com/file/shyewduv7h5ws23/FAT32_formatter.exe)
IMPORTANT NOTE: this USB stick must have at least 256 MB storage capacity!

3. Extract the ZIP archive content to the formatted USB stick.
4. Rename "$SystemUpdate" to "$$ystemUpdate".
5. Go to NXE by booting up your Xbox 360 while holding RB on your controller or by pressing  XBOX  > "Settings" tab > "System Settings" (select "Yes" if asked "Are you sure you want to exit?") >  B 
6. Insert the USB stick in your Xbox 360.

There are different messages that can show up now:

1. "An update has been found. To apply it, you need to restart your console. Do you want to restart now?"
   Select "No" and double-check the dashboard and the downloaded update versions. If no mismatch is found, try reflashing your NAND and retry these steps.
2. "To proceed, security and program updates are required. System updates will be added to ensure security and proper functionality. If you decline, you will be returned to the Xbox Dashboard. Do you want to accept the update?"
   Select "Yes" and wait for the installation to complete. Your Xbox 360 will restart when finished.

Done!