Step 1: download the tool PROTECTION ID from
http://www.cdkiller2002.tk/
Step 2: scan the main exe of the game you want to copy with the downloaded tool
(I think Generals is Safedisc2 protected, but scan it!)
Step 3: Read the FAQs on top of this board! Specific the part about the protection the game has.
Then you will have the wisdom to make a 1:1 backup.