Microsoft is said to be working on a 100GB hard drive for the XBox 360. It is interesting that Microsoft have to "work" on this since it is just a SATA notobook hard drive. At least there will finally be a reasonable capacity drive may be available.
It would be a tactic of m$ to make their internal drives in a fashion that would make it more than difficult for u to replace whatever drive they put in the box with one u can buy from u`r friendly component supplier.