Installing and Setting up Xfce

Xfce is a fast alternative desktop environment to KDE and Gnome. It is great to use on older computers. It doesn't contain a full set of applications like Gnome or KDE, so you will have to use external applications instead. It also doesn't include a login manager.

Installing Xfce

Installing Xfce is easy. Just do
pacman -S xfce4
You will want to install all of the packages in the group because just about all of them are necessary for Xfce to run normally. You will also probably want to install extra applets for the panel and plugins.
pacman -S xfce4-goodies

You will need to install a web browser, because Xfce doesn't provide one. Have a look at the web browser part of the application recommendations guide.

You will also need to install a login manager. SLiM or Xdm is good for Xfce because they don't have any KDE or Gnome dependencies. If you have Gnome or KDE installed you can use GDM or KDM respectively.

Configuring Xfce

Firstly we will need to open up your /etc/rc.conf as root. On the DAEMONS line add the following:
DAEMONS=(...fam hal..)
You will need FAM for keeping the desktop icons refreshed and HAL for automounting.

If you have only one user on your computer, you can use your /etc/inittab to login to your user automatically. Open your /etc/inittab as root and change the following lines:

# Boot to console
id:3:initdefault:
# Boot to X11
#id:5:initdefault:

to

# Boot to console
#id:3:initdefault:
# Boot to X11
id:5:initdefault:

and at the bottom
x:5:once:/bin/su [insert your username here] -l -c "/bin/bash --login -c startx >/dev/null 2>&1"

If you want a login manager to start up instead, uncomment the line with the login manager on it.
Example
If you are using SLiM for example, uncomment the following line:
#x:5:respawn:/usr/bin/slim >& /dev/null