I will be going over how to install XBR and Xell onto your Xbox 360. Installing XBR allows you to do many things such run unsigned code(homebrew), install any sized hard drive(even 3.5in desktop hdds!), ftp into your box, and custom dashboards. There are endless possibilities with being able to run any code you want. You are able to modify Xbox 360 games to run custom maps and cheats. You can also launch games off the hard drive without a disc. It should cost you around $5 in parts, maybe even free if you have the parts already.
Step 1: Finding out if your Xbox is exploitable
Your kernel must be kernel 2.0.7371.0 or lower for this to work. You can do this by opening up the system info tab. After there is one more step to check if it still is exploitable, but you have to build your cable to dump your nand first.