Aurora R4, no video, no BEEPS

Hi folks, I'm in trouble with my 5 years old Aurora R4 PC. A week ago it went down and after trying to power on I can not see anything on my monitor. No Alienware Head, no picture. Monitor says, the cable is connected, but no signal. Tried to get POST information but no BEEPs, no other error message. I did some troubleshooting steps, but no idea about the problem. 1) I have removed all memory modules, pulled out disks and DVD, removed the video card (GTX-970) as well After power on I can hear 2BEEPS -> Space -> 2BEEPS -> Space -> 2BEEPS continously. All FANs and lights are UP, and runing 2) I have done PSU test (test button on the back side of the PSU) - it looks OK (Orange LED lights as well at the MIO board when the power is ON) 3) Put 1 memory modul back in, in DIMM 1. No BEEPS. Nothing. I tried each of the 4 sticks. 4) I have reset CMOS (with battery pull and jumper) and no change. 5) I have replaced CMOS Battery as well - Result is same. No BEEPS, no video 6) Tried 2 other working video cards. Result is same. No BEEPS, no video I'm suspecting, it can be CPU or MotherBoard problem. It sounds bad. :-( Do you have any other idea? Many thanks in advance: Atti