Configuration is stored in "c:\Documents and Settings\Username\Application Data\codeblocks".
Replace "Username" with your username.
I'm not sure if "Application Data" is the right name for the subdir, because I don't have an english installation at the moment, but it should be something similar.
You can delete the whole "codeblocks" subdir, and than you can start with a really fresh C::B.
By the way: never edit "default.conf" by hand.