If its one of those early super socket 7 or slot-1 motherboards with an AT and ATX power connector then you might have issues powering up or have a wobbly/noisy picture, otherwise it shouldn't be a problem.
Oh dang. When I power up my pc, the back fan moves a little bit, the CPU led turns red for half a second, and I get no image on my monitor. The only way I can reset it is buy actually powering off the power supply.
have you fitted stand-offs between the mobo and the back plane?
I'm really sorry, this is only the second rig I've ever built. What specifically are standoffs? Is the board shouting out or something?
standoffs create a gap between the motherboard and the backing plane, they are needed, and are included with the case, and possibly the mobo. what you are experiencing could be caused by a short