After reading your post i was a bit confused on which medium was used where. Did you try both original and backup on your pc or just one. Did you try both or just one in the computer your friend has. If both original and backup work in your pc the backup is probably good. Did you try the original in your friends? If you get an error off the original in your friends it might be an error not associated to the backup.
*I have C&C generals and its the biggest btch to install I thought. It took me 3 days of messing with the config file to get it going. You need latest drivers on video card, sound card, monitor, and latest directx. In my case I even needed to adjust my refresh rate. Well I am not going into my thoughts on how lazy programmers are getting and how hardware is ahead of software so min requirements shouldnt be anywhere near what they are now for games.