Im not sure exactly what you mean, but if you have a save file on your hard drive then it doesnt matter what disk you use. Save files are on your hard drive not the disk itself.
You lose your unsaved progress. :)
You don't need live to save games to the hard drive the game will simply ask you to create a new games save and off you go. If you have a memory card too the game will give you a choice of which device to save your game on.
Saves your game information, and your xbox live account.
The hard drive on your xbox 360 is the optional storage device which stores all your saved game progression, music, pictures and games.
You buy the game from a store and put it in the drive in your Xbox 360.
It basically saves files music & game data outside of your internal drive so you can take it places or give your friend music or game data it's just a big memory card for the xbox360
No. Removing or inserting a hard drive from your 360 whilst a game is in progress will cause your 360 to restart.
yes ofcouse
no
you cant yes you can! the only thing is that if you made a new account then there isnt... but if you were able to just upgrade you account all of your crap is still there. however progress you made on a non-live game will not be transferred to you live one. ie: if you play MW2 and get to level 70 split screen it doesnt transfer to xbox live.
xbox360
the best game for xbox360 is either CALL OF DUTY 4 or GTA4.