How to find which version of Drupal I'm running?

If it's available, go to Administer >> Reports >> Status report. This will list your version number if you have Drupal 6.0 or later. In Drupal 5.x and earlier, the path to go to is Administer >> Logs >> Status report.

Failing that, look for a file called CHANGELOG.txt in the root of your Drupal directory and open it up to find the version you are running.

If CHANGELOG.txt is missing, you can also check in system.module for a line at the top like:

define('VERSION', '5.5');

If this is present, it will tell you which version you are running. If not, you have a version earlier than 4.7.2.