It is my understanding that the most important part of the TASK29 process, is the command that the executable sends at the conclusion of the flash process. Without a file to flash, the process will not execute, thus folks started out with radio files and then settled on a boot image as the least intrusive flashable object. So, if you extract the nbh from a task29 self-extracting archive, you'll more than likely end up with an *.nbh object, which consists of a boot splash screen.
I'd love to be corrected if I am wrong, but this is my understanding.
Best regards,
-boggsie
<edit> and this probably should be merged on to the end of the existing thread which covers task29 ...
http://forum.ppcgeeks.com/showthread.php?t=116571