I've seen laptop drives between 9mm and 18mm thick. I believe most are now 10mm thick. Thicker drives allow more platters and higher capacity. Of course if all you can find is 10mm thick drives, that's what you're stuck with. Otherwise, you could find out if your lappy supports thicker drives by pulling the old one, I've seen some laptops use spacers to fit a thinner drive into a taller space.
<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>