How is your Xbox modded? If it's softmodded, which softmod? If it's flashed / chipped, which BIOS? How did you configure the softmod / BIOS - all F, or F and G?
How did you build the 500G disk? How did you format it?
Where are you putting the application? When you say "it does not show on the Xbox", what do you mean? Does it not appear on the disk, or does it simply not appear in your dashboard menu?
Next time you start a new thread, try using a more sensible title and providing a bit more information......