Hey folks... this was easier in CS1 and previous, but I was curious as to how to change defaults in Illustrator CS4? For example, I've customized my brush library and want to replace whatever the default brush file is with my customized brush file (for now, called, interestingly enough, brushes.ai) Where is the location of the (default brushes) file? Thanks!
You can place your custom created files to the location
\Program Files\Adobe\Adobe Illustrator CS5\Presets\en_US\Brushes