Disk backup??????

Im running Windows XP pro on a 1600+ AMD Athlon,
I bougth a $50 game wich me and my brother use a lot, I want to make a backup so we can use the backup in stead of the original, but when I actually finish the backup, the files are there but it doesn’t autorun, I mean that when I try to play it doesn’t recognizes the backup only the original, but all info is there, same amount of MB but it just doesn’t work, I need to know how to make it work, do I have to rename or add a file or something likethat????
Please help!
Thanks guys!
MDL3