You probably could overclock it, but as buwish said, OC'ing a laptop, especially one like that, is a recipe for disaster. I think you could change the BIOS to do it, but you'd probably need a really nice cooler and a self-made heatsink system (copper blocks and stuff). Even then, what would you really get out of it?
About getting past the mobo limited to 2.8, I don't know how to get by that. But really, that limit is probably there so people don't fry the mobo by OC'ing it too much.