Switch Off Post Revision In WordPress
Post revisions, a new feature in WordPress since version 2.6, may be just what you were looking for but they are not for everyone. They can cause database bloat and slow posting.
One thing the writers seemed to have forgotten is an easy way to switch off the feature. Luckily its not difficult:
To turn off this feature, add this following code to wp-config.php:
define(‘WP_POST_REVISIONS’, false);
Via How To Turn Off Post Revision In WordPress 2.6 (it also shows how to delete all the old revisions too).