If you want to run a modern system with an old computer you have to compensate some of the missing GHz and megabytes with your own brains. You have to know what you are doing. You have to know what you want your computer to do. Only so you can build a system that is ideal for your needs and your hardware.
This means you have to be ready to learn something about Linux and how it works. It is not rocket science, it is something everyone can do. If you are willing to learn you can realize the full power of Linux.
We are lucky to have a lot of free documentation. There are even many good introductions to Linux. Most of them are published by The Linux Documentation Project. I suggest you first familiarize yourself with the site just to see what kind of documentation there is. Depending on what you already know, select some of the guides where you can learn at least something new. If you are relatively new to Linux, you might start with Gareth Anderson's GNU/Linux Command-Line Tools Summary or Machtelt Garrels' Introduction to Linux - A Hands on Guide
TLDP is not the only free source of information online. The Linux Cookbook has been one of my favourite Linux books since years. Michael Stutz has released the first edition of the book as an HTML edition. Even if it is already several years old, it is very helpful for those willing to work on the command line. In this book, the reader learns about basic command line operations, process management, text processing, customizing the shell prompt, analyzing text, finding text and files and a lot more.
If you want build a custom system and not use some lightweight distribution, you have to study a bit more. One of the sites I have found most useful, is the Gentoo wiki. It has been most helpful also at times when I have used some other distribution. For example, if you want to learn how to customize some lightweight window manager you will probably find all the best tips and tricks there. One good example is the page for tweaking Openbox window manager. Most of the information here can be used with just about any distribution.
Other tips are probably more obvious: If you are using any Debian based distribution, for example Ubuntu, you should study the Debian reference. It has been translated into many languages. Slackware Linux Essentials - The Official Guide To Slackware Linux is similarly useful for those who use a distribution based on Slackware, for example Zenwalk or Vector Linux.
If you read the fine manuals, you will be able to solve most of your problems. If not, you can always ask for help in the Internet forums or IRC channels. But if you have done your homework the others will respect you more and be more helpful than in the case you never bothered to read any documentation. But as you are now reading my blog, you most probably are clever enough to read some official documentation!
