How would you format the hard drive to change the

Hi,

you can,t. the only option is a replacement Drive.
Even then if it,s been serial Logged to M$ site. your original gamer tag et,c may still be active and logged to the console itself.
There are ways and tools to Format The drives, but has to be re-partitioned to specific sized Partitions, For The 360 to recognise It.

Mike @ Compurepair.