Shutdown when switched to battery instead of sleep

Hi, how would I get my mac to immediately shutdown when it goes to battery (it's a laptop) instead of sleeping once the battery runs down? The laptop has actually been turned into a server and I'm using the battery as a UPS of sorts. Also, is there a script somewhere that is executed before a mac sleeps that I can edit to have it shoot off a email in the event that it does go to sleep? Thanks! 🙂

The laptop is running 10.4.11.