Before I proceed any further; flashing your bios incorrectly/incompletely CAN and most likely WILL render your machine useless. The information which I am providing worked/works on my specific machine. 

Now to the task at hand. Having only OpenSolaris on this machine and wishing to update my bios firmware I had two choices:

• use a recovery disc I made after purchase, which would entail installing Vista for the sole purpose of this procedure
  
• use a usb stick with the needed bin on it and flash from that

I chose the latter and here's how I did it:

1. Download the spXXXXX.exe from hp site
   
2. unpack the .exe using cabextract
   
3. rename the extension from xxxx.FD to  xxxx.BIN  /* x = the alphanumeric string proceeding the extension */
4. insert USB key ; cp xxxx.BIN /media ; umount /media  ; shutdown
   
5. Remove the battery from the unit
6. Unplug mains
7. Hold down 'Windows' and 'B' keys ; re-plug mains and press power button
8. After the flash completes and before the machine starts, remove the USB key
9. Done