How to start clean install again?

[Jay O'Brien]

What's the best way to erase an installation of FreeBSD 
completely from a HD and start over? I'm installing 4.10 
from am ISO CD, and it installs fine. However, I would 
like to start over from scratch and it "remembers" some 
of what was on the HD from the last install. If I were 
in Windows/DOS I would just "format C:" but that doesn't 
seem to be an option here.

Jay O'Brien
Rio Linda, CA  USA