Yes, you can delete the default characters if you don't use them.  You can also do a "minimal install" instead of a full one. I used to do that with Poser 5 and 6 when I had a smaller hard drive and didn't have room for a full install.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi