As far as I'm aware, once you send someone a file on CD, there'll always be a
way to get to the files. However, if you're concerned with your PPT file
being accessed, your best bet is to apply security settings.
Which PowerPoint version are you using?
Try Tools > Options > Security tab > Password to modify
Additionally, you can apply a password to open.
This will require it to be opened as Read-Only as well.
Cheers