Intel mobo help needed. PLEASE HELP

Hi there, im a newbie here!
but iv got a serious problem. Need a big help from u guys.
I have an Intel D945GCcr mobo with intel p4 3.0 processor and kingston 1G RAM.

I'v been using this machine for 3 years now. And there were no big probs except for lil things till yesterday.
Last night i switched on the machine but it went off in nearly 5 secs. So i checked it again, nothing worked except cpu fan and other fans. no signal on monitor, no power LED. Hard drives were not spinning. And DVD/RW's LED was not blinking, but there were no beeps either. I checked for some time. Nothing happened.
So i removed the mobo from the casing. And got it out and removed all the connectors except for two power connectors and the power switch connector, then i turned it on. but nothing changed. same things happen. but i heard a small clicking noise (like the sound we hear when a HDD starts) from the mobo speaker. (dunno its really the speaker, i think it is) that's it and it went off again.
I removed the battery for sometime. but no change.
And there was a one special thing. when both the IDE and power cables were connected to DVD/RW it was not working(light was not blinking and couldn't eject the tray) but when i removed the IDE cable it worked. I was able to eject the tray.

Please guys help me to find the problem. is it on the MOBO or on the PSU? Please help!
Thanks in advance!

Hard to say. I generally replace both at the same time after a board failure or change. It's good insurance. What ps do you have? List the wattage, brand, 12v rail rating and age.

Can you borrow a good PSU and try with it?