The next steps are very dangerous if you missed something you can lose your game saves or the HDD!!!
60GB XBOX360 hdd is not recommended!!!
You need the full game to play this addon.
1, connect your xbox360 HDD to your pc with a HDD Connectivity kit
or unpack your HDD case and use a simple sata cable.
2, turn on your pc and boot a windowsXP (only works with winXP!).
3, run "Xplorer360_09b6_20gb.exe" or "Xplorer360_09b6__60.120gb.exe" depending
on which size of HDD you have.
4, choose Drive -> Open -> Harddrive or Memcard... option.
5, after it loaded choose partition 3.
6, open the "Content" directory and inside open the "0000000000000000" directory
7, you have to open all the subdirectories of "0000000000000000" to find the
installed GTA4 files. That directory what you looking for contains lot of
files all of them with 162MB sizes (Data0000, Data0001, ...) PICS/2.jpg.
You can find that directory easly if you install only the GTA4 to the HDD.
8, when you found it you have to MAKE a NEW FOLDER which name is "00000002"
under the GTA4 directory in this case under "545407F2" directory (PICS/1.jpg)
9, then open that new folder , right click on mouse and choose "Add..." option
to add the "B66716ED23BE790FCF1210AB932119501DC7405E54" file.
10, after the copy finished close the program , and turn off the pc.
11, connect xbox360 hdd to the xbox360.
12, insert GTAIV disc and start the game.
(on the first start you need xbox live connection)
13, then come an update and you have to apply that.
14, restart the game
15, when loading it will checked that a "DLC" has been downloaded. It is ok.
16, Enjoy it