I've made it no secret that I have several old computers. While they may not be as old or cool as what you guys have, they're still pretty decent for day-to-day tasks. Today, I'm going to teach you how to repurpose any old (Made from 1998-2004) computer as a pretty decent little machine. Once you get older than that, you start going down the slippery slope of window managers and CLI-only use. While I may not be the expert of that, there are other people who can teach you how to get a few more years out of that Pentium 1. Once you start getting into 486 territory, it's obvious that you want to be featured on Hack A Day, rather than use an older computer.

Assuming you have aquired such a machine, the first step is choosing a Linux distribution for it. Windows is too bloated and unsupported on older machines, and Mac OS X is even worse, especially on PPC. Due to these reasons, my iBook runs Debian "Wheezy" 7. I'd recommend you read the Debian Installation Guide here if you need some help if you also decide to do this with a PowerPC computer. In fact, I'd run Debian on ANY machine because it's stable, relatively lightweight, and supports almost any processor architecture. Here's what you need to do if you're installing Debian.

1. Download the netinstall image for your processor architecture here. Burn it to a disc and install (You'll need to have your computer directly connected to an ethernet cable). Once you get to the part where it asks you what collections of packages you want to install, deselect "Debian desktop environment", but select SSH server and Laptop, if you use a laptop. The rest of the steps should be self-explanitory.

2. Log in as root, install sudo (apt-get install sudo) and add your username to the /etc/sudoers file by typing "visudo" and under "root ALL=(ALL:ALL) ALL" add "[Your username] ALL=(ALL:ALL) ALL". Save and exit.

3. Log out by typing "logout" and login to your user's account. From there, type "sudo apt-get install lxde" to install LXDE, a lightweight GUI. You may also want to add whatever graphics and sound drivers you want, if they weren't installed already. Just search the name of the component and "debian" to see if anybody else has gotten it working.

4. Reboot. You're done! Now, install whatever packages you want from LXTerminal in the Accessories menu. Copy the line below (one line) to get the package of software I use.

sudo apt-get install iceweasel sylpheed transmission pidgin gftp libreoffice libreoffice-gtk qpdfview feh audacious vlc pcmanfm fotoxx leafpad synaptic

Iceweasel is Debian's version of Firefox, Sylpheed is a lightweight email client, Transmission is a bittorrent client, Pidgin is a chat client, gFTP is a FTP client, Libreoffice is an office suite, qpdfview is a PDF viewer, Feh shows pictures, Audacious plays music, VLC plays video and audio, PCManFM is a file browser, fotoxx is an image editor, leafpad is a text editor, and Synaptic is a graphical version of apt-get. You'll want to keep the system updated by running "sudo apt-get update" and "sudo apt-get upgrade" in the terminal once in a while.

5. The great thing about Debian is that any applications that are open-source and run on Debian will run on any processor out there that Debian supports. Here are some of my favorite games that run on my iBook:
Bomberclone: A clone of Bomberman
DOSBox: Emulates almost any DOS game out there.
FreeDOOM: A free, GPL Doom WAD that you can play with PrBoom.
LBreakout2: A Breakout/Arkanoid clone.
OpenTTD: An open-source version of Transport Tycoon Deluxe.
Pingus: A Lemmings clone.
SuperTux: A Super Mario Bros. Clone
glTron: A game that lets you play the Light Cycle game from Tron.

Thanks for reading this far. Please don't turn this into a technical support area. If you have trouble with Debian, ask the people at Debian's forum, which can be found at forums.debian.net.