Every CD-R has important info on the disc itself which is called ATIP or pre-groove. Without this data/info the CD-R cannot be used by a writer. The ATIP contains the following info:
- The capacity of the CD-R
- The manufacturer of the CD-R
- The type of the CD-R (eg. Audio only)
- Supported writing speeds
- Absolute lead-in time
- Last possible address where data can be written[li]etc...
Only a CD-Writer can read the ATIP (because like I said before this ATP is only needed when writing a CD-R). The ATIP protection is based on this fact: when the game starts it checks if there's is ATIP info present: if so then it will presume it's a CD-R disc and will not play. However a normal CD-ROM cannot read this ATIP and will of course 'say' that this data is not present: thus the copy will work...