Just going to add this. How old is the laptop HDD? if it uses the updated standard SATA connections then it's got the same plugs on it as a 3.5" drive and works no different. The only difference between desktop and laptop drives is their size and maximum capacities.
But in the sense of just moving it over and booting up the OS you have on it then that's not going to work as the version of Windows (assuming you are going to be using that OS) is the kind that doesn't like changes in hardware and thusly when putting into a different system with different hardware it just simply won't work.