Can't boot up Xserve G5

I have a xserve G5 with Mac OS X 10.3.9, with the following hardware specs:

CPU: Dual PowerPC G5 ( 3.0 )

L2 Cache ( Per CPU ): 512KB

Memory: 2GHz

Bus Speed: 1 GHz

Hard Drive: 250G

1 Powersupply

3 GiG Ethernet Ports

2 USB Ports

1 Video Card

It was running OK, but for some reason, I can't boot it up recently after a few days offline. the system identifier light is on yellow ( no blicking/flashing, constant yellow). According to the user manual, the yellow colour of this light indicates:

"There is an alarm condition in the server or someone has turned on the light manually; check the server monitoring application for more information."

But I am no idea what could be the problem as I can't see any display by getting the server connected to a monitor directly, even the hard disk light is not on. I can hear the noise though after pressing the on button and the noise gets stronger after a few minutes ( BTW, the enclouse lock is not engaged.)

I have also tried to hold the system identifier button while pressing the on button to enter into the firmware boot commands,where I can start from either the CD rom or make the xserve to target disk mode, but it didn't work.

Any ideas would be appreciated.

Cheers,