Enigmah's Video Select 2 is a tool that will allow you to switch your Xbox's region from NTSC to PAL or from PAL to NTSC.
Switching the region is useful if you have a PAL Xbox, as when you switch to the NTSC region the Xbox is then capable of outputting at 480p, 720p and 1080i with the use of the component cables.
This is great for homebrew apps such as XBMC as they will upscale video to 720p so SD content will look a lot nicer on your HDTV. Some, but not many Xbox games also support 720p, such as Soul Calibur 2. Many games will play perfectly in 480p however, which looks a lot more clear on a modern HDTV.