The details pane shows you see the most common properties associated with the selected file. File properties provide more detailed info about a file, such as the author, the date you last changed the file, and any descriptive tags you might have added to the file.
You can adjust the height of the details pane in Windows Explorer by dragging its top border up or down for the size you want. This is also a global setting that gets applied to all explorer windows in only your user account.
This tutorial will show you how to reset the height size of the details pane in explorer back to default for your account in Vista and Windows 7.