around 6-8 gb I believe Another advantage is that if the disc has a scratch in it, since it is loading the game data from the hard drive, your game won't crash in a section where it would normally read the scratched part of the disc
"Kill all of the enemy units because their red color advocates communism. " -Albin0
It's 6.9GB install. The xbox doesn't sound like the space shuttle on take off,the load is a tad faster(maby),and it's less wear and tear on your xbox. If you really care go spend $20 on an 8GB flashdrive and install it to there.