Recently I had a project where we needed to switch from a standard Drupal 7 site configuration to use an install profile instead. This was done to facilitate core and contrib updates via Drush.

Prerequisites

• an install profile that you wish to switch to
• an existing Drupal 7 site
• Drush is installed on your environment
• Registry Rebuild is installed on your environment

To set the install profile of the site, simply run drush vset --exact install_profile {YOUR_INSTALL_PROFILE}

Make your install profile the active profile in the database:

UPDATE system set status=0 WHERE name='standard';
UPDATE system set status=1 WHERE name='{YOUR)INSTALL_PROFILE}';

Then remap modules and themes to use their appropriate analogues in the install profile. Rebuild the registry by running drush rr. Now all references to sites/all/modules are replaced by profiles/{YOUR_INSTALL_PROFILE}/modules.