Instructions
Load the "Call of Duty: Modern Warfare 2" game disc on your Xbox 360 console and join a multiplayer match. Before joining, make sure "Sentry Gun" is selected in the "Killstreak Rewards" menu.
Play the multiplayer match as you normally would. Once you get a 5 kill streak, a pop-up message will tell you that you have earned a Sentry Gun.
Press the right side of the D-pad on your controller to select the Sentry Gun killstreak reward and then push the right bumper to throw a green-smoke signal grenade. A chopper will now fly by and drop the Sentry Gun to you in a box.
Press and hold the "X" button to capture the Sentry Gun, press right on the D-pad again to select it, and then pull the right trigger to place it in the desired location. Your Sentry Gun, or Aimbot, is now placed and you have the ability to modify its location to a different spot, if desired.
Walk up to your placed Aimbot/Sentry Gun and press and hold the "X" button to pick it up. Walk to a new location and pull the right trigger to place it in the new spot. Your Aimbot/Sentry Gun's position has now been modified and you can modify its position again whenever you want.