Thans! I doubt that it will work because the PowerMac seems to stop booting at an early stage (it couldn't boot to Open Firmware). I tried it once, and it didn't work, although it makes the chime of "resetting PRAM". After a few strikes, it boots up to a retail Tiger CD by pressing the "C" key.
Great news, so did you get it running?
Might be time to replace the PRAM Battery, 4 years is close to their lifespan, far less if ever without AC power, & can cause strange startup problems...