I found this in a few different places around the 'net - hopefully it's helpful:

Use the Address Bar to Launch Programs or Web Pages

Windows XP Professional enhanced the functionality of the Address bar to make it easier to launch your favorite programs. You can add the Address bar to the taskbar on the bottom of your desktop. Then you can launch programs simply by entering their names in the Address bar.

For example, to launch Calculator, simply enter calc in the Address bar. Anything you would normally enter in the Run box on the Start menu can be entered in the Address bar. The Address bar also lets you quickly go to any Web page you specify.

• Right-click an empty area on the taskbar.
• Point to Toolbars, and then click Address.
• Open the Address bar by double-clicking it.