Depending what your definition of "reset" is, there are two operations for the 4400:
System Control Reboot: Resets all units in the stack simultaneously.
System Control Initialize: Initializes every unit in the stack to factory default settings.
This should be covered in the documentation for the 4400. If you have none, I would suggest you go to 3Com's website and download the manuals.
Happy reading!
....JIM....