http://supertrick.net/tutorials/softmod003.asp It is for a softmod but the process is the same for a chip mod. If you have a chip you can skip the locking step.
a good point to remember too is, that if you formatted a hdd on your pc, you would have to create a partition, (using dos /fdisk etc) if the hdd doesnt have one. if you have a modchip installed, the very easiest way to do it on your xbox, is via an autoinstaller.