hard drive save?

[osugsxr]

recently my cod mw2 was scratched up by my nephew while he visited. Well game didnt work, took it to gamecrazy and they were able to fix it! Thanks to them, anyways I was told to save the game to my harddrive, took up about 6gb of space.
Is this correct, it doesnt matter if the game is scratched or anything now, as long as I play it from my hd it will be fine?

 

[Cheadyp]

When you start a game that is installed to your hard drive, the Xbox 360 does a check to make sure the game disc is in the tray. If the disc is scratched so much that it is unreadable, you will not be able to play the game, because it will not be able to tell if the correct game is in the tray.

Though, there is a benefit to having the game installed. If the game is not installed and your Xbox 360 gets bumped while the disc inside is spinning, it will sometimes leave a big scratch in the disc. But by having the game installed to the hard drive, you mostly avoid this problem since the disc will not be spinning while you are playing.