Often to learn Linux and older computer – what might be called a "throw away computer" can be or is used. After all you will have to complete your standard computer and online tasks while you become "proficient" handy and familiar with the Linux operating system. It all takes time. On top of that you may rescue more than one computer from the landfill.
Older less demanding versions of Linux distros are readily available in newsgroups and online. These are either referred to as "older version", "archived editions" or "legacy" versions.
The questions become – what are the hardware requirements of these older Linux versions. In most cases you will want to start your Linux career with what used to be referred to as "WIZIWIG 'graphical interface now known in a standard fashion as a GUI (Graphic User Interface) and to what most people and computer uses now know and use as either the Microsoft Windows Line of products – Windows 95, 98, ME, 2000, XP and now the newest version of this OS line – Microsoft Vista. way up to the current Mac OS X in its various forms. The key is that by using a Graphic User Interface – the GUI – your life is easier – well at least for learning Linux. to make things happen. The inner workings of Linux – with its typed or keyboarded commands are still there under the surface. Linux is a most powerful computer language. Knowing the actual commands makes Linux a most versatile and powerful operations system. You may want to learn Linux by command line rather than the windowed environment. If you do that is a good thing. However the commands may not be familiar to you in any way and manner. Further if you do not type exactly right and correctly – in the right order and in the right syntax nothing will happen for the most part from your computer commands. You will just be dead in the water so to speak and frustrated as well.
While it is possible to install really older versions of Linux on what might be called "primitive computer hardware" – such as 386 and 486 with 8 or 16 mbs of ram, this is not generally recommended. If you want to run the GUI setups of Linux you will need more more powerful setup. It can be done on a Pentium (first generation of the current Intel Pentium line of computers). What will be referred to as a "Pentium" computer is the first generation Pentium computer, which the computer chip maker Intel, introduced in 1993. Pentium computers run up to speeds of 200 MHz. As time went on later and more powerful computers were released as the Pentium 2, 3 and 4. Typically a later number of Pentium computers will be faster than a previous number. For example a Pentium 3 will generally beat out any Pentium 2 computer in speed and power. There is a second computer chip maker – AMD, as well as Intel in the computer CPU chip marketplace. For the most part, in terms of your early Linux career, either Intel or AMD processors are equivalent and interchangeable for you, for all intensive purposes. The point for you is to get the most current and powerful computer if you want to learn Linux with a GUI. A newer computer will handle the graphics better, may allow or even require a newer version of your chosen Linux distro, and overall will be much faster and easier for you to start your Linux career with.
Lastly to install Linux you will need a working CD Rom (CD burners and DVD optical drives will do as well), and a Linux supported video graphics card.
Used computers are like a used sailboat. The previous owner most likely paid a fair bit for the device, knows it is worth much less on the marketplace and overall just wants their older or previous computer to go to someone who can make good use of it and enjoy what was their older computer and its hardware.
By installing and learning Linux on an older, even a throw away PC computer, you may well be rescuing the computer from a fate in a landfill. Well at least for now.