Afraid he's right, the A7m doesn't support overclocking via the multiplier. There is a mod for the board that involves adding dipswithches and replacing resistors, but I wouldn't try it unless your really good with a soldering iron. From what I've heard there have been a good many boards ruined trying it. You can try upping the fsb, provided you have quality ram and your pci cards can take it the board seems pretty stable at high bus speeds. Or you can try changing the multiplier by changing the bridges on the cpu itself. I like my A7m, it's a great board, it's just missing one vital option.
Also, I don't believe it's a micro atx board Andy, mines pretty damn big, biggest MB I've ever owned actually. Unless of course you meant something else, I get confused easily =]