probs 1:1 dvd backups, diff files sizes

im trying backup a game simpsons hit and run
prob is the games around 6gig and when i try transfer it to pc it only does 2gig but says all files transfered.
i burnt the disc but it dosnt work so how do you get the missing files when they dont even show up.
this also happened to me on the game enter the matrix
lil help, thanks!