Intel 845 GL mother board no display ;processor memory & SMPS are working fine in another mother board

Does it have any beep sounds on switching on( some computers won't produce beep sound) or does your monitor is not getting any signals from computer even though it is ON and has shown any message or menu screen of Monitor functions then,
You will be having a faulty RAM or your Graphic port has some hardware malfunction.Or it can be also from a new unsupported hardware installation that will prevent computer from booting up.

If your monitor does not provide any of the above monitor functions successfully then
It would be a monitor problem. Check wires or cables of monitors or contact nearby technical support