Hide the common dialog back button
User Configuration\Administrative Templates\Windows Components\Windows Explorer\Common Open File Dialog
Removes the Back button from the Open dialog box.
This policy, and others in this folder, lets you remove new features added in Windows 2000, so that the Open dialog box looks like it did in Windows NT 4.0 and earlier. These policies only affect programs that use the standard Open dialog box provided to developers of Windows programs.
To see an example of the standard Open dialog box, run Notepad and, from the File menu, click Open.