You can install Ubuntu, by doing this:

PLUG IN AN EXTERNAL MONITOR FOR INSTALLATION AND FIRST BOOT SETTINGS

or

1. Insert your Ubuntu install disc (or usb drive) and reboot.2. When you boot the disc or usb drive and you see the "Purple Ubuntu screen" or Ubuntu splash, right away, hold the Fn button and dim your screen brightness then brighten it back up. If you forget to do this and the splash (or purple screen) is gone then the back-light probably wont work and you can't install Ubuntu.

Once ubuntu is installed and you boot from the HDD, do the same when you boot Ubuntu. When you see the purple screen, right away Hold Fn button and dim the screen down and up. Most emachines, being made by acer, to do this, hold Fn button and then hit the left arrow key then the right arrow key.

Now, that's a bit annoying to fix, and once Ubuntu is booted, you can't adjust your backlight. What we want to do is make ubuntu turn the backlight on automatically when you boot it and also, allow you to adjust your backlight once Ubuntu is booted. To do this:

1. Type in terminal: sudo gedit /etc/rc.local

Find the code :

exit 0

Above exit 0, put in:

setpci -s 00:02.0 F4.B=00

Save the file.

This fix will automatically make the backlight turn on upon boot.

Now to ensure you can adjust your backlight once Ubuntu has booted:

2. Type in terminal: sudo gedit /etc/default/grub

Find the code : GRUB_CMDLINE_LINUX=""

Change that line to: GRUB_CMDLINE_LINUX="acpi_osi=Linux"

3. Type in terminal: sudo update-grubWait for the process to finish then exit terminal. Reboot your PC.