Unity GNOME KDE XFCE LXDE

*Unity

Recommended System Requirements for Unity

Required RAM	1 GB
Required CPU	1 GHz

http://askubuntu.com/questions/22402/will-ubuntu-11-04-work-on-my-old-pc


*GNOME

Recommended System Requirements for GNOME 2.x

Required RAM	384 MB
Required CPU	800 MHz

http://linuxreviews.org/software/desktops/

Recommended System Requirements for GNOME 3

Required RAM	768 MB
Required CPU	400 MHz

http://fedoraproject.org/en/get-fedora

*KDE

Recommended System Requirements for KDE

Required RAM	615 MB
Required CPU	1 GHz

http://itmanagement.earthweb.com/osrc/article.php/3930006/GNOME-vs-KDE-The-Latest-Round.htm


*XFCE

Recommended System Requirements for XFCE

Required RAM	192 MB
Required CPU	300 MHz

http://wiki.xfce.org/minimum_requirements


*LXDE

Recommended System Requirements for LXDE

Required RAM	128 MB
Required CPU	266 MHz

http://lxde.sourceforge.net/about.html