I have a backup of Battlefield 1942 that I made and I was testing it. I installed but the game woulnd't start. I made sure that I had Safedisc emulation turned on, and tried many times and it still didn't work. Then I put the original cd in, played for a few minutes, quit, and now the backup works.

A simliar thing happend when I was testing another program that has emulation.

Why does this happen technically speaking? If I need to have the original CD in order to get the emulation started, then I am screwed if the original gets destroyed and I only have the backup?