One of the new features in ArcMap and other ArcGIS applications is the ability to execute multiple tasks while something is processing in the background. This is called background processing. If enabled, you can have a process running while navigating throughout the ArcMap interface. You might recall in the 9.3 version, if you were processing something, you were not able to do anything at the same time. This wait time is typically felt when processing large complicated polygons or raster files.
If you are scared of this background processing and prefer the former “pop-up-window” you can disable this background processing function. Simply go to Geoprocessing, Geoprocessing option and uncheck the background processing (indicated in the video).
Certainly, there is nothing to be afraid of, when it comes to the background processing. With the new version 10 interface, many functions are dynamic in addition to a locking feature for actively edited files. In many of my videos, you will see that I will be running foreground processing since it is easier to monitor process status.