Watchdog in Arduino Library - or at least support by bootloader

Nick, thanks for your reply. Ummmm... how do I actually load this? Using the Arduino IDE under tools->Burn Bootloader ? Obviously from my question I've never done this and would appreciate pointing me in the right direction. Is there documentation you could site? All I could find in http://arduino.cc/en/Guide/Environment using IDE tools->Burn Bootloader is:
"Ensure that you've selected the correct board from the Boards menu before burning the bootloader."

Thanks in advance.
Rich