New machine will be here tomorrow.

FYI - When you download something from Xbox Live, the DRM (digial rights management) will only allow the content to played on a specific piece of hardware. In theory, any DLC can be placed onto the HDD. The DRM signature will look for the machine the HDD is attached to.

If you were to take your existing HDD and pop it onto another machine, your DLC will not work. You'll have to re-download everything and go through some obnoxious back-route to get some of this stuff to work.

If the HDD to other machine is permanent, you'll have to pass your digital content's rights to the new machine. This can be done via PC (xbox.com/drm) & 360. When the 360 signs onto XBL, the webservice will then accept the new machine as being the primary. You'll then have to re-download everything.

You can only do the DRM transfer once-a-year and this is only good for gaming. Movie licenses do not transfer.