I don't know where the OP is, so I didn't get too specific, but as ksandness alluded to, there are stores in akiba that do sell north american electronics. I've also seen stuff in den-den town in Osaka. But they're mostly duty-free places, so look for duty-free signs. They come with english Windows and everything. =) I remember specifically having to avoid those places when I was buying a netbook, because I wanted a japanese one. =D

That being said, amazon is another good suggestion. I've not shopped on amazon.jp for laptops, but I'm guessing you could find a north american laptop there.