I think the Aug 28 1997 firmware was the first that could boot from a BSD
filesystem. You should also be able to dir c: or dir d: (though this is
a bit flakey and I think only came in with Sept 17 firmware).

For ZIP disks you have to dd zeros to the first 512 bytes of the disk as
well as adding a valid disklabel. Im not sure if this is true for hard
drives as well, but Id not be surprised. 

If you have a new firmware image you can upgrade to it over the network 
with the net-flash command. This reads a file rom.DNA from the tftp server 
that would usually supply the bootimage, then (with/without checks depending 
on version) it erases the flash and writes the new version. Of course 
if something bad happens at the wrong time you need to pull out the chip 
and use a prom programmer. You can also upgrade from a ZIP (or presumably 
a hard disk) if you get the new firmware there. Im not sure that this 
is an official thing to do, you have to mutter a bunch of forth! 

Mark