Dell Dimension 9150 Does Not Power On

Hello:

I have a Dimension 9150 the USB ports on front IO board failed so I replaced it. Along with he cable. Now when I try and power machine on nothing happens, When power is applied fans spin up. LED on system board is green, There are LED's behind RJ 45 connector they flash Yellow Orange, Orange.
Have tred removing all memory no go.

Any ideas?

Gord