Boot Fail!

[Technogeek]

Hi Guys please give me a clue to what to look at nest.

I have a sapphire MB here with an AMD2 socket, It was working fine until I changed the heatsink/ fan for a water cooler.
Now after I installed the water cooler Corsair H50, I turned on the PC but the no beep and post, nothing on screen just the whering of fans. I know that it is either the CPU or the MB but can't put my finger on which one.
I have swapped out CPU with a known working one but that did not help. I also put this CPU in working MB but quickly realised that the MB was too old for the CPU and no BIOS upgrade was available, so no boot their either.

Please give me a clue to want to do next as I am doing this for a friend and he wants his PC back asap.!

[3DWizard]

If your old CPU also doesn't work now, it could well be the mainboard. Test your components in a different system too.