Just wondering if there's a way to force my ibook to boot from a firewire hd.

Booting from a FireWire device: Nearly all "onboard" FireWire equipped Macintoshes (except the Blue & White G3 and some early G4s "Yosemite versions") are capable of booting from a FireWire disk, provided that your Macintosh has ROM firmware 2.4 or later. If your Macintosh ROMs are not 2.4 or later or you are unsure which ROM firmware you have, you should download the latest Apple ROM updater utility from http://docs.info.apple.com/ article.html?artnum=75131. Macintosh models which have FireWire disk devices connected to PCI FireWire adapter cards are not capable of booting. This is a hardware limitation, not a FireWire driver limitation. In addition to your Macintosh's ability to boot from FireWire, the firmware on the FireWire bridgeboard (inside the drive case) must also have bootable properties. Unfortunately, some don't and no driver can resolve this limitation. If you are unsure, contact your FireWire disk manufacturer to find out if yours does.

I can boot from firewire. But what I'm asking is...is there a way to force a firewire boot by holding a button or something while booting up.

if you can still get to the os on your primary os you can choose the startup disk there under your startup options if you cant depends on the os if os x i can help earlier i cant (i can get you to a console prompt on the os where you can manually edit the startup configuration (osx is bsd at the core)

Not sure if this would work since I've never tried it, but try holding down the "Option" key during startup. In New World ROM machines, this will force the machine to look for any bootable volume and display an icon for each one it encounters, sort of like a GUI boot menu. If the FW disk appears (as it theoretically should assuming that your Mac has native FireWire), then simply click on the icon and click the arrow that points right to boot to that drive. -Chad

http://lowendmac.com/tf/010419.html