Alienware Aurora R4 not booting

A few days ago my pc started to not boot at times and had a continuous 1 beep for motherboard failure. But when this happened if I turned it off and back on again it would boot about 50% of the time. Sometimes it booted straight away without getting stuck at POST.

I thought there was a wire that had come loose or something so I opened the case and all I did was check to make sure most of the cables were plugged in and I took out and put the PCI fans cable back in again. That was all I did.

Now when i press the power button it seems like its turning on normally at first (power button light is on, fans start up, case lights come on) but then that's it, nothing else happens. It doesn't beep at all and nothing appears on the screen.

I did some looking around and ended up taking the CMOS battery out and putting it back in again after a few minutes, nothing changed.

Then someone said take all the RAM out and see if it beeps. So I did and the motherboard does beep twice for no RAM.

Any help will be greatly appreciated