Chicano :
That (14 x 12 x 7 inches) measurements is incorrect... the standard MATX size is 9.6 X 9.6... they can be narrower or wider but the Height determines the form factor and this one looks 9.6 inches in height and apprently the same wide. You can tell from the 4 expansion slots and the lenght from the I/O edge to the mobo bottom. In ATX the I/O edge is only half way to the bottom of the motherboard. And you can only measure motherboards in H X W so what measurement would the 7 inches represent?. probably 7 centimeters to the top of the CPU fan.
Note that USAFRet only said it appeared to be mATX, as it is considerably smaller than a standard ATX board.
This is not a standard consumer board for seperate retail however, and likely does not have a standardized size board due to the fact that it comes from a Dell prebuilt system.
I don't know about you, but that doesn't look like an ATX board to me!