you can try the flags/settings of other 5970 owners here https://en.bitcoin.it/wiki/Mining_hardware_comparison
some of them get up to 800 mhash/s

as for the alienware laptop, there is a chance of it overheating if you run it 24/7 so maybe only do it a few hours per day.

ps
seriously you have a 6970, try crysis instead of dota