EasyDeleteConversation makes it more convenient to delete conversations, by adding a delete button after the preview of a conversation in /messages/all, instead of forcing the user to enter a conversation delete it, go in a different conversation, delete it, etc. etc.
Place the unzipped plugin folder in your
vanilla/plugins folder and then activate using the Dashboard.
If you don't like the look of the delete button, you can change the CSS in design/style.css