To use the Android 2.2 port for A5IT, you need your device to use the multiroot facility from OpenAOS. This allow your device to boot any image from a shiny bootloader.

download the needed files from the archos homepage

• download the SDE firmware, rename the file firmware_archos5.aos to sde_archos5.aos to avoid confusion
• download the regular 1.9.xx Android firmware from archos (you can use 2.0.xx if you want but you will encounter problems with video playback in the archos media center)

You now have one file named firmware_archos5.aos which is the original android os and one file named sde_archos5.aos which is the SDE containing anstrom.

compile aos tools (instructions for Ubuntu 10.04)

sudo apt-get install libssl-dev (if you have not already done it)

svn checkout http://aos-tools.googlecode.com/svn/trunk/ aos-tools
cd aos-tools/libaos
make
cd ../tools
make
sudo cp aos-unpack /usr/local/bin/

unpack original firmware

aos-unpack /path/to/firmware_archos5.aos

Of all the files unpacked, the following are of interest:

• ./firmware_archos5/root/cramfs/androidroot.cramfs.secure
• ./firmware_archos5/root/cramfs/bitmapfs.cramfs.secure

we will need them later

flash the SDE

Before you install the SDE, please make sure your device is either running a 1.9.x or 2.0.x firmware. There have been problems reported with directly going from 1.7.x to the new SDE AOS file (the ubi-fs was damaged and ubi modules were not loading).

Copy sde_archos5.aos via usb the root of your device, after unmouning cleanly, execute the update via the archos file manager.

Angstrom will boot afterwards, it takes a long time. Be patient. You will have to create an initial user account and set a password.

install the boot menu

• Reboot your device while holding down the [VOL -] button.
• Press the [VOL -] button 5 times to reach the “Developer Edition Menu”. Then Press [Power]
• Press the [VOL -] button 2 times to reach the “Flash Kernel and Initramfs” entry. Then Press [Power] ONCE. Wait 2 seconds.
• The screen now should say “connect your device…” – Please do so and mount the device on your desktop PC.
• Now get the following files and put them on the root of your archos device:
  •  initramfs.cpio.gz
  •  zImage
  •  menu.lst
  •  ubitools.tar.gz
  •  script
• Copy the previously unpacked androidroot.cramfs.secure and bitmapfs.cramfs.secure into the main directory of your device.
• Unmount the device safely. (Else you might damage the files!)
• Press the [Power] button – The screen will flash briefly and say “Kernel and initramfs updated”.
• Press the [Power] button – The device will now reboot.
• The Boot menu should now appear. Select Ångström or just wait 10s.
• Press Other then Root shell – a root terminal appears
• Now execute the following command with the on screen keyboard:

   . /mnt_data/script 
  

• Now reboot the unit and go back into recovery (see step 2, this time select “Access HDD using a PC“)
• Connect it to your Linux PC and fire up a partition manager
• Make sure you are editing the right drive!
• Create an new ext3 partition in the empty space at the end of the drive. Make sure it is created as type primary and is the second partition (e.g. /dev/sdc2)! The unit will not boot Android if the partition is e.g. sdc3 or sdc5!
• Now mount that partition and copy some of the remaining contents of the firmware onto it (lang*.alz and the upselling directory)
• Unmount the drive and reboot your Archos device.

Congratulations you should now have an dual-booting gen7 device!

The original instructions are available on this  blog entry, I copied and pasted most from there.