So my best bet is PC6400? Even the 'raptor's made for laptops are 12mm?
Actually, I wouldn't change the RAM at all. PC-6400 will not work natively because the chipset does not support it. You can only reach DDR2-800Mhz (PC-6400) by overclocking the FSB, and it depends heavily on your machine how far you can get it. My Atom N270 goes to 2.1Ghz (FSB 173Mhz), but there are others on this forum that don't even get passed 1.9Ghz. Either way, the RAM module that's inside the N10 is actually already a PC-6400 module, it reaches those speeds without a problem.
About the Raptors: There are no Raptors for laptops, there's only one series Velociraptors and they're all 2.5". Standard laptop drives are also 2.5", but as I've said the standard thickness is 9.5mm, where the Velociraptors are 12mm thick. The reason why Western Digital made the Velociraptors in this smaller form factor is because 2.5" has a higher data density (the platters are physically smaller) so it makes them faster AND cooler (platter is lighter, less weight for the motor) than standard desktop HDD's that are 3.5".
Don't make me "touch" you :-D