CUSTOM COMPUTER CASE help me find correct size?

The computer I currently have is:





Acer AMD Phenom X3 Triple Core 8400 2.1GHz Computer (AM1201-E1721A)





I would like to know what size type the motherboard is [ATX etc] so I can buy a bigger case. I will be buying the case from tigerdirect so any suggestions would be appreciated. Thanks!CUSTOM COMPUTER CASE help me find correct size?
I have checked the specifications given by Acer but they do not give any information about the type of motherboard. There is a method of determing the type of motherboard which involves placing the computer sideways such that the side with the motherboard is closer to the floor and then looking into its back. If your computer has an ATX motherboard, the expansion slot covers should be on the right. If your computer has a BTX motherboard the expansion slot covers will be on your left. The positions are seen when looking into the back of the computer. Your computer will most likely have an ATX or micro-ATX motherboard. A micro-ATX motherboard will fit into a case for ATX motherboards but not the other way around.