I agree with Smartmom, I'd go the smarter way and get a smaller, cheaper internal for the laptop, and then use the extra money on an external giant drive. I just got this Seagate 2TB External Drive and LOVE it. 2 Terabytes is enormous. And I bought a 15ft USB cable that I just use to switch between my desktop pc and laptop so I don't even have to move the drive around. The only 'drawback' to it is it has to use a wallwart for extra power, the USB power isn't enough, and there's sometimes a very short pause, when opening up a file manager, like Explorer, or PowerDesk while it enumerates the drives, due to basically pulling the external out of a slumber mode once it's gone into it. When it's not in slumber mode it's just as fast as an internal drive while enumerating the drive letters. Transfers themselves are as fast as an internal hard drive.

I also have a Seagate 500GB External drive which doesn't need the extra power and there's no slight delay when showing the drive letter in a file manager. It's an awesome drive. But since I got the 2TB drive I no longer really needed it for my regular computer stuff so I use it for my DVD Player. And for that it ROCKS!