try and set your power settings to automatic. that way when unplugged the CPUs will be clocked down. also, what are u trying to do during lap use? if u only really use it plugged in then it will be running at full boar and be more likely to heat up. if u r doing only casual stuff on the lap when plugged in, just click on the battery icon up top and set it to a lower setting. if u r doing anything disk or CPU intensive like video editing or games u basically need a laptop stand of some sort. also, the more insulation in the fabric the notebook may be resting on the hotter it will make the notebook. i.e.-i can be casually using my iBook seemingly forever w/o it getting hot or the fans kicking on if i'm on the couch wearing jeans or whatnot. on the other hand if i'm kicking back in bed and have it resting on my lap on top of a down comforter the fans will kick on eventually.
let your computer breathe.