No Beep, No Boot HELP!!!

I turned on my PC and everything came on except the display on the screen.(Icon says no Connection).

I opened the PC and the Fans were spinning, HD seems to be ok as it is making a spinning sound, Fan on Video Card is spinning but there is no LED light coming on the Mobo and there is no Beeping noise from the Mobo when I turn on.

I replaced the Mobo and PSU but it is still the same. but I was and still am a bit unsure about the Panel 2 config, I couldn't get them going but I changed around the cables and the PC Power came on.

I removed the battery for a minute and replaced it. I removed every possible part there is from the Mobo and reseated everything one by one to try to eliminate, when I removed the CPU I noticed that the Coolant Gel was a bit thin looking.

Is there anything else I should be doing when installing a new Mobo? All connections are solid and I don't want to be spending money on the wrong parts. Please Help ASAP.

The Display and the Cables are fine as they worked on another PC I have.

Could it be the CPU? Memory? Video Card?

Thanks.

Specs are 2x512 MB RAM
Intel Celeron 3Ghz
350W PSU 230v
128MB ATI Video Card

First of all get a friend and test every compenent in his computer and if you don't find anything wrong check the mb with case conection power switch, reset switch, etc.
Is you mb 775 socket. Because you must plug the 4pin cpu power connector like the p4 cpu, if that aint plugged your computer won't start normally.