SD2 is a software protection being placed upon newer games. There are only a few titles out there that currently have this protection, about 12 or so, but more are on the way. These games include, American McGee's Alice, Hitman Code 47, Red alert Command and Conquer 2, and a few others. The big problem is that plextor and a few other manufacturers are "selling out" so to speak. One of the problems with SD2 is that even though CloneCD and other software claim to be a 1 to 1 copy, which for all intents they do just that, the BURNER itself must do a scramble on the bad sectors before burning any data to prevent bit sychronization because household burners can not do an unassigned bit very well. What SD2 does is force a bit sycronization when the bad sectors are scrambled. The only burners out there that don't scramble the bits around are acer, philips, and a couple plextor drives. With the plextor drives though the problem lies in the firmware. Any firmware update after 1.04 forces the drive to scramble the data while earlier firmware updates don't. Also to prevent people from using the older firmware with newer drives the eeprom for the firmware has changed. 1.04 and older firmware is 530kb while newer firmware is 440K. With newer drives having only 440kb available, using older firmware is practically impossible. If you want to learn more go to
Game Copy World and read a bit more about safe disk version 2 software protection. You can also look on the Clone CD clinic site (forgot the address since it's at home) and search the forums there.