Abstract: Various technologies and techniques are disclosed for aggregating and using data collected from multiple computers to modify a later behavior of those computers. In one implementation, a data aggregation system is described. A data collector is operable to collect behavior data over a network from one or more applications used by the computers, and to save the behavior data to a data store. A data installer is operable to access the behavior data in the data store and convert the behavior data into a format that will modify a future operation of at least one of the applications that is used on at least one of the computers. A method for creating and distributing a custom dictionary from data collected from multiple computers is described. A method for identifying related documents from data collected from multiple computers is also described.