Autamtic reports created by the system?

Hi, we suddenly have a lot of reports that were apparently automatically created by the system and which we do not need (most of we do not even understand as they do not relate to our use of Sugar at all as we are not a sales company e.g. "Pipeline according to user"- whatever that means). These needlessly clutter up our report list, so why were they created and how do I make sure that when I delete them they do not just pop up again and again?