Here is some information via a Japanese press release regarding the Xbox 360 120GB hard disk drive to be released with the Elite. It turns out you can’t do a lot of things with it, and there are quite a few setbacks.

• You can only move data from the 20GB Hard Disk to the 120 GB Hard Disk. Transferring data in the other direction, or any other combination, is not possible.
• Any data stored on the 120 GB hard disk will be automatically deleted.
• Any data stored on the 20 GB hard disk will be automatically deleted after it is moved over.
• You cannot put the data from two or more 20 GB hard disks onto one 120 GB hard disk. If you attempt to move multiple drives, only the last one you move will be stored.
• Once you move the data over, it cannot be placed back on the original hard disk.

Microsoft had originally advised 360 owners to buy two 20GB hard drives to fit all of the available content. It turns out that you can’t put data from both drives into the new 120GB, so this pretty much means a lot of angry gamers.

Read (WIRED)