In Windows you have always had the ability to personalize the background, fonts and some windows display elements for some time. However, with Windows 7 the ability to create your own themes was taken a step further.
In Windows 7 not only can you create your own cycle of desktop wallpapers and pick your own Aero shading color to enhance the desktop but you can save your work and share it with others.
If you spend a lot of time looking at your computer screen, you know how important it is to like what you see. In Windows 7, you can change the desktop background, window border color, sounds, and screen saver to suit your style—by creating your own theme.
This page shows you a video overview and then provides you step by step instructions on how to create, save, share and remove themes in Windows 7.
I have used these methods to create my own collection of themes and you can see those efforts and try them out yourself:
Windows 7 Themes