In System 7 Pro, Apple added a new feature to the Finder, namely highlighting the destination window on drags. This feature was added in a very intelligent manner though. Examine the following picture sequence.
Notice how that, in the first image, the Finder does not highlight the Games window because it's the original window. This means that you can move objects around in the window without being bothered by the highlighting. In the second image you can see the highlighting is applied when you drag into a different window. But now, if you drag back into the original window, you will see the highlighting is present (as shown in the last picture).