Learn to create custom themes for your desktop through three fantastic tutorials. First up we have RocketDock which allows you to bring Mac OS X to your PC. You can create your own icons, manage programs, it’s completely customizable and easy to use.
Next up we have Samurize, another solution for desktop customization. It allows you to monitor various aspects of your PC through widgets along with plenty of other features.
Finally, we have a step by step guide which guides you through the process of creating your own themes (one of which is featured above).