Even some GIS Administrators do not know about this one.
C:\Program Files (x86)\ArcGIS\Desktop10.0\Utilities (on Windows)
Advanced ArcMap Settings tool
I need to update this http://mapperz.blogspot.com/2007/02/esri-arcgis-92-tips-and-tricks.html (just don't the have time, anyone can update - will re-post with full credit)