All you need is an old PC, high-speed internet, a router or switch for multiple computers, and PATIENCE.
Images WILL BE UPDATED LATER!!!
Step 1: Get the computer!
I found mine in my step-mom's office.
Step 2: Install Linux
With Ubuntu Feisty Fawn, if you use a PC made in 1999, the motherboard year checksum might fail. Anything made before 1999 might need to run 6.10 or lower.
Step 3: Install the Server Software
Now download the file to your computer (duh)!
To install, go to a Linux shell (Terminal) and login as the system administrator root:
su(If you don't know the root password, or if one isn't set, you quite obviously have administrator rights, so you can change the root password from your account. If you need to, go to Settings>Users and look for the user "root". Double-Click on it and change the password.)
Then extract the archive to /opt:
tar xvfz xampp-linux-1.6.3a.tar.gz -C /opt
(The extract command didn't work for me, so I just extracted the files with the default archive manager in Ubuntu straight to /opt)