Retired Documentation: You are using the documentation for version 1.7.3 which was retired in 2013. Go here for the latest version documentation or check here for your available upgrades to the latest version.
Data Pruning
Control Panel Location: Admin > Utilities > Data Pruning
This section of the Control Panel allows you to "prune" or remove old weblog entries, comments, forum posts, etc. based on various criteria. Each page will present you with various pruning options.
Be careful using this feature as it will permanently remove the data from your database. You are encouraged to backup your database before using this feature.