Change Magento Default Theme

# Modern
cd /var/www
/var/www/pear mage-setup /var/www
/var/www/pear install magento-core/Interface_Frontend_Default_Modern

System > Configuration > Design > Themes
Default: modern

# Blank
cd /var/www
/var/www/pear mage-setup /var/www
/var/www/pear install magento-core/Interface_Frontend_Default_Modern

System > Configuration
General > Design > Themes
Default: blank

# Links
http://www.magentocommerce.com/design_guide/articles/working-with-magento-themes#head-say-hello-to-multiple