Suppose you wanted to put some demos for an unmodded Xbox 360 on an external hard drive, how exactly would you do it? Would you just add them inside a folder named content/0000000000000000/? Or is there more to it?
You can't without having a jtagged Xbox 360. You're best bet is to just use a large (8GB) USB flash drive.
So I suppose that the fact that I'm plugging it in via USB (and it gets recognized as an external storage device) doesn't help? Thank you for your help.
You can format any USB hard drive to work with the Xbox 360, if you go in to memory management you can configure 16gb of that usb hard drive to work with the 360. If you had say a 500gb drive you could still only use 16gb of it, which is why its better to use a USB memory stick like KingBurns suggests. This program can inject demos in to it once formatted by the 360: Xbox 360 USB Storage Xplorer - Xtaf v32 Beta 2