Rather than using a hardware button, or downloading the XP-style on/off/reset app, why not install an app specifically designed to perform a soft-reset when run? I use Philippe Majerus's RESET app.. it's tiny (5K), saves wear-and-tear on your hardware switches, and takes significantly less memory than that other app.
http://www.phm.lu/Products/PocketPC/Other.asp
PM also has a SUSPEND program that mimics the behavior of the on-off switch. Again, it's tiny (5K) and doesn't require you pressing a hardware button. I have RESET sitting in the Programs | Accessories folder, and SUSPEND in my main drop-down menu. Use the ARM version of both, they work great!