I'm helping my brother find a motherboard/processor combo for his Northgate computer. He bought a motherboard/combo (celeron 2.8 ghz) for an ATX case from Microcenter & it didnt fit. He's thinking he needs a micro atx. I'm going through the manual & it looks like it's a P4XMS main board. My question is, how do you specify what type of motherboard he needs for the case he has. Any advice would be appreciated. Thanks.