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 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 in the next step

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.