T7400 workstation new motherboard and still won't boot !!!

Hi Folks,

My T7400 Workstation was giving me a bad memory error (2 risers 32 GB each for 64 GB) and after a time then started to throw the bad memory error and failed to boot at all with that beep post code saying bad RAM.

I went and got a new motherboard and dropped it in tonight .... no more memory beep problems but now it turns on - everything starts to whirr away and then it all quits and shuts down but just the Video card fan keeps running.  The yellow light is on - on the MB.  No beep or post codes ......

So what am I doing wrong?  I only have the open on-board board slots filled  ( all 8 ) and I'm n not using any riser cards just to eliminate any problems ...... and no luck.

Hopefully one of you experts has a idea because I'm out of them :-) 

Cheers'

Dave