defecetd motherboard

hi to all..

i had a computer that unable to run. when i repaired it i found out that the motherboard was defected coz i tested all the peripheral being attached in the computer and it was function normally. my question is, can ask you a tips , how to trouble shoot the motherboard? is there any site that can help me to trouble shoot the motherboard?.

thanks so much..

your answers are highly appreciated

john