Socket 462 motherbord

Hi
I have removed and replaced the same CPUs on 2 462 socket motherbords
arrow pointing wright way round and frits and fitted back the fan
neither of them now work they ever power up for a few seconds and switch off or dont power up at all
and refuse to prossess one has a beeper on it and sometimes makes a constent beeping noise
I have replaced loads of CPU in the past and i have never had such a stuip problem putting the original CPU back

Any advice please

Thanks
Toolless