Instructions
Insert a FAT32 file system USB flash drive into any of your computer's USB ports.
Click the "Download Update" link in "Resources" and scroll down the page to the "To install the update from a USB flash drive" section.
Click the download link in the "To install the update from a USB flash drive" section to download the update file, and choose to save it to your computer.
Open your USB flash drive by clicking the "Start" button on the desktop, selecting "Computer" and double-clicking the flash drive icon in the computer window.
Double click the update file (named "$systemupdate9199"). The file is a zip file, but operating systems such as Windows XP, Vista and Windows 7 will unzip the file automatically. If you are using an operating system older than Windows XP, use a program like WinZip to open the file.
Click and drag the contents of the update file to your USB flash drive. Do not remove the USB flash drive until the file transfer is complete.
Eject the USB flash drive from your computer and insert it into any of your Xbox 360's USB ports.
Power on or restart your console to begin the installation.
Choose "Yes, update now" when prompted.