U.S. patent 6,727,830, granted April 27, is described as a "time-based hardware button for application launch."
The patent abstract goes on to explain that the patent relates to how different functions can be invoked depending on whether a button is clicked once, clicked and held down for a period of time, or double-clicked within a short period of time.
A Microsoft spokesman confirmed that the patent was granted by the U.S. Patent and Trademark Office to Microsoft and that it was developed by employees working in the company's Pocket PC group. He couldn't say whether or not the patent applied to desktop applications, or how Microsoft planned to enforce the patent. For more info, click here!