Xubuntu is an official variant of Ubuntu
which is specifically targeted at old or low-end
machines.
This is primarily achieved by using the Xfce
desktop environment rather
than the memory intensive GNOME
or KDE.
Memory requirements are
also reduced by using mostly GTK+ 2, helping to reduce the number of
libraries. This helps to reduce the memory requirement to
just
128 MB RAM, significantly lower than Ubuntu
or Kubuntu.
To run the Desktop CD (LiveCD + Install CD), you need 128 MB RAM to run
or 192 MB RAM to install. The Alternate Install CD only required you to
have 64 MB RAM.
About Xubuntu