Transbar

Transbar is a very simple utility that adds transparency to the taskbar, without the need for additional software tools and without offering any other feature.
The application is extremely easy to use and that's most likely the reason why the developer hasn't included a help file as well. It all comes down to the slider that allows you to configure the transparency level and that's basically it.
The main window is very simple and holds the aforementioned slider plus a dedicated tool to launch Transbar when Windows starts. Additionally, there's a separate feature that offers you the option to enable or disable the application on the go, without asking you to modify the transparency level back to the default setting.
Transbar works on Windows XP and older versions of Microsoft's operating system, and that's quite obvious since Windows 7 comes with a built-in tool to add transparency to the Taskbar.
Just as expected, Transbar remains light on computer resources all the time and system performance isn't affected at all after applying the modifications.
If we were to vote for an improvement, we would most likely choose a System Tray icon that would allow users to control transparency quick and easy, but also dedicated controls to disable or enable transparency straight from this icon.
Overall however, Transbar offers users one the things they like the most: transparency. And since it works with Windows XP and doesn't hamper computer performance at all, you should really give it a shot.