One brilliant thing about Linux is that it can be tweaked anyway to suit any kind of a system. If your system is pretty old and if ubuntu is too slow in it, then here you go. LXDE(Lightweight X11 Desktop Environment) is a light weight environment that's fast even on antique systems. It is surely not designed to be powerful or bloated but it is light enough to keep the system usage low.

Not all components are integrated but most of them are independent and each of them can be used with a few dependencies.

Here are some of the important LXDE features :

• It's lightweight and runs with reasonably low memory usage.
• Fast and runs on old machines producced in the '90s.
• Gook looking gtk+2 internationalized user interface.
• Desktop independent(every component can be used without LXDE)
• Standard compliant, follows the specs on freedesktop.org

Installing LXDE in UBUNTU:
This first step is to edit the "/etc/apt/sources.list" file. Add the following lines to the file.(Please make a back up before you do so)

For hardy heron users:
"deb http://ppa.launchpad.net/lxde/ubuntu hardy main
deb-src http://ppa.launchpad.net/lxde/ubuntu hardy main"

For gutsy gibbon users:
"deb http://ppa.launchpad.net/lxde/ubuntu gutsy main
deb-src http://ppa.launchpad.net/lxde/ubuntu gutsy main"
Save and exit the file.

Now the source list has to be updated. Open a terminal and type the following command:
sudo apt-get update
Use the following command to install the LXDE environment:
sudo apt-get install lxde

This will install all the required components for LXDE. Now you need to logout from you system. Then go to Options->Select session.

Select the LXDE option and click on Change Session.

The following screen allows you to select if you want LXDE environment as your default or only for this session. Select what you desire and you are logged in to the light weight gtk+2 desktop environment!!!

source : ubuntu geek.com - http://www.unix-tutorials.com/go.php?id=3712

cheers
aravind
:)