The short answer is, if Sony couldn't come up with a 100% foolproof copy protection, neither will you.

(And BTW, they brought on themselves a lot of trouble trying to do so).
It IS possible to make it more DIFFICULT to copy for those not savvy with computers. Mind you, if something can be played, it can be copied. Nevertheless, look here:
http://en.wikipedia.org/wiki/CD/DVD_copy_protection
Good luck.
[EDIT] Another link you may find interesting:
http://forum.videohelp.com/topic341418.html