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!