This is a discription of a minimal grafic Ubuntu system on an old PC with a harddisk of 1.2GB and 128MB ram (an old win98 PC ?)
Boot from an dapper (6.06) or a edgy (6.10) CD,
Choose for installation of a text system, commandline system or server install (so not the 1st option !).
After the installation and rebooting your system, you have a minimal Linux system, running Ubuntu from the command line.
Type: sudo nano /etc/apt/sources.list
remove the "#" in front of line beginning with"deb".
With "cntrl X" and after that "y" you can save the file on your harddisk.
Type: sudo apt-get update
The list of available program's is now updated.
Now you must install the following programs with the command
sudo apt-get install <program-name>
x-window-system-core You need it, if you want a graphical system. gdm Gnome Display Manager, to log in to. xfce-panel Fast and small window manager. xfce4-goodies Extra program's that you'll need. xubuntu-default-settings XFCE setting, so you can start after installation. xubuntu-system-tools To make life easier ... samba Sharing files with Linux and windows computers. ntp-simple Synchronize time and date. synaptic Install software in a graphical way. thunar File manager, you can's without. mousepad Simple good word processor. update-manager Automatic updates for your safety.
It is possible to make a script that will install all of these for you, put the following commands in that script file:
sudo apt-get install x-window-system-core sudo apt-get install gdm sudo apt-get install xfce-panel sudo apt-get install xfce4-goodies sudo apt-get install xubuntu-default-settings sudo apt-get install xubuntu-system-tools sudo apt-get install samba sudo apt-get install ntp-simple sudo apt-get install synaptic sudo apt-get install thunar sudo apt-get install mousepad sudo apt-get install update-manager
Now you can tweak you're system and modify it tha way you want, the result is a small fast and stable Linux system with a graphical desktop
If you also want a web-server than you need to install apache2, if you want also PHP support, you need to install libapache2-mod-php5.
Don't put a (my)sql server on it, it will slow down you're system too much.
There are a lot of things you can do with an old PC, this is just an example.