Thank you for the clarification :-)
I agree that shooting from the hip is not a good approach - I did however, contact Microsoft before I wanted to start replacing my hard-drive and did get the answer (my first post) that it would violate the XBox-live agreement. It was not their legal department though, but their tech support (who might have gotten the instructions by their "boss" to always give that answer, true or not).
I also agree that it's "my" hardware, so I should have the freedom to do what I like, unless it's to intentionally harm a company (like Microsoft) financially (ie. illegal games etc), and not have to be ripped off for something that should have been possible/there to begin with.
Anyhow; thanks again for the clarification - no offense taken. :-)