I think I understand more of what you're asking, but let me know if I'm off here.
Personally, I think that things have changed now, and it is MUCH easier for little kids to get their hands on porn, especially if their parents are not vigilant in paying attention to what their kids are accessing on the internet.
As for the CDs that I assume that he burned, or someone burned, it means that he took a bunch of jpgs/gifs, and because he wanted to save them, he burned them to the CD to keep. So, in essence, he puts whatever images he wants to put on there. If he got a bunch of images from a website, and he wanted to save them, instead of keeping them on his computer, he put them on the CD to archive, give to someone, backup, or whatever. This would not be a CD that he bought with images already on it; he puts things on it himself.