Save the environment
You can also help to save our environment by using your old computer or by using recycled hardware. Nowadays, computers that have very low power consumption (less than 10 W) are also available for public. This usually means their specifications are rather low on modern standards. Thus information on this site could equally well be used for building a usable desktop on such a box. Using low specs or recycled hardware is truly green computing, a part of modern and sustainable way of living.
Also modern low end computers are often used for running Linux. Ultraportable laptops by Asus have Xandros Linux preinstalled on them. Linutop is a small low end desktop computer designed for Linux. Users of this kind of computers can also benefit from reading this blog.
Is it worth the trouble?
Only you can decide, whether to install Linux on an old computer or to recycle it. Even if you have another, modern desktop computer, you could use the old one with Linux. You could use this as a learning experience: you will learn a lot about how the operating system works. This knowledge can be useful, and learning is always fun!