If it works, as in plays back and records ok, then you probably won't ned to upgrade the HDD.
At least if I'm wrong, it's something that can be done easily later on but I wouldn't jump the gun.
I can't speak for windows 7 and the us-1800, but now that the info is up maybe someone else will know.
I'm a little out of touch with windows, but there's still a 32bit or 64 bit option right?
Which are you installing?