XBOX 360 HARD DISK PROBLEM?

Im using the old xbox 360 dat came up with 12gb hard disk and i juz bought new 120gb hard disk. how can i transfer my saved game to the new hard disk? can i like, load any save game using the old hard disk, n when the game prompt to save the game, i juz replace to new hard disk? does this have any effect on my xbox? many thanx in advance