It depends on what you do with that laptop. If you are gaming... I wouldn't want a 5400 drive, especially not in HL-2. The whole power sucking heat producing monster theory that people believe about 7200 drives has been debunked several times.
Go with a 7200, you will notice a sharp difference in performance for games, and you will lose hardly any battery life. If you do lose any you'll gain it back in load times (more time playing less time waiting) As far as heat... don't even think about it much less worry about it.
As far as the RAM speed, DDR2 would be better, but it's not a huge deal if you chose a rig w/o it.
Oh and BTW.... it's a laptop not a labtop.
/end thread