Power off on shutdown -h

[Ben Paley]

Hello,
	I've been trawling documentation and newsgroups for a while, but I don't 
really know where to look - I want to make my machine turn itself off on 

shutdown -h now

If I turn it off by hand at the switch then, when it boots next time, the 
BIOS thinks it's corrupted and spends ages sorting itself out (dual BIOS). 
The other solution is to do

shutdown -r now

and reboot to Windows and shut down from there... unsatisfactory, I think 
you'll agree. Can someone point me in the direction of something useful?

Cheers,
Ben