my xbox 360 is moded, i dont play xbox live.also my xbox 360 is the arcade version so no harddrive, anyway i have the original gta4 (not downloaded from net), and when it got backed up i tried it and some wierd glitched kept distrupting my missions.i.e,bulding getting blury,walls taking a long time to appear.the original one worked fine, so i gave my original copy to this guy mods xboxes and he copied it for me making sure there no mistakes despite that the backedup version of gta4 is still the same problems.the man told me that it is because a harddrive is larger space and the game is more smoother than playing with memory card, or it might be your laser when reading a disc however the original works perfectly so how can it be the laser. i highly doubt it is got to do with getting a harddrive. plz if anyone got dis problem or anyone who has got some advice do share..sorry about the legnth.