Removing my gamertag/friends list/etc. from my 360 hard drive?

[64Bits]

Any help with this? I'm probably going to be selling my whole premium package to someone locally within the week, but I would like to know how to delete everything off the hard drive, if possible. There's a bit of time left on my xbox live subscription, but I would prefer to not allow the person I'm selling it to to have access to that stuff. Any suggestions?

[segagamer4life]

easy, go under the last blade, system I think it is, and click on the storage/ hard drive option, click format, and all will be gone. I am oversimplifying a bit, but it is real easy from where I am directing you.