I would check the BIOS options to see what it's got for boot devices. I thought it was possible, but I found this on Maxtor's website:
"It is not possible to boot to any Windows® operating systems from any USB or 1394 external storage unit. The only bootable devices that can be configured from the BIOS is SCSI, IDE, Floppy, or CD-ROM. The option to boot from a USB or 1394 device is not available.
FireWire booting is possible on all Macintosh models that have built-in FireWire ports with the exception of the Power Macintosh G3 (Blue & White) and the Power Mac G4 (PCI Graphics) models. The rule is: "you can boot from a 1394 disk if your system shipped with MacOS 9.0.2 or later". The operating system version on the 1394 disk must be 9.0.2 or above."
I honestly think it has more to do with the motherboard BIOS than anything. I would bet a newer mobo with builtin firewire has the option to do it.
Augie