There is a very good article about how to manage the LCD backlight of your Dell laptop

I’ve tried it out and it works very well.

DivFix++ designed to repair broken avi file streams by rebuilding index part of file.
This program is very useful when trying to preview movies which has no index part,
like some files are currently downloading at “eMuLe”

How to install DivFix++
Either download the package from here or add the Treviño’s Ubuntu Repository to your /etc/apt/sources.list by:
deb http://download.tuxfamily.org/3v1deb feisty 3v1n0
deb-src http://download.tuxfamily.org/3v1deb feisty 3v1n0

and install it via APT by:
sudo apt-get update
sudo apt-get install divfix++

This repository has many other packages included and worth to have a look at them

On Ubuntu Documentation you can find the CompositeManager/Xgl Howto for Ubuntu.

There is also an howto on the official Beryl Homepage: Install Beryl on Ubuntu Feisty with XGL – Beryl Wiki

Complete How To: Dell Inspiron 6400 also covers the setup of Beryl on Ubuntu.

If you want to use Beryl instead of Compiz you need to extract beryl-xgl from http://ubuntu.beryl-project.org/pool/feisty/main/0.2.0/beryl-core_0.2.0~0beryl1_i386.deb and copy to /usr/bin. You can refer to this bug for more details.