Well...
You *could* shoot the user. That could work.
Kidding aside, you could, at least for text boxes and tables, use Javascript to make it much harder to do. Problem is, users can disable Javascript. You could require Javascript and only display the values in those non-copyable regions if Javascript is enabled. But clever users could then leave Javascript on to render the content, then turn it off momentarily to copy it.
You could also put your content into images or a Flash movie. Then only the images would be copy/past-able. But then it wouldn't be text-boxes or tables?
Things can get more complicated with frames because, depending on your particular needs, you don't necessarily have access to the content displayed inside the frame.
So, all things considered, I like Lorraine's answer better; you can't.