W2k Pro, Windows Explorer refresh.

In w2k’s windows explorer (nt explorer, file manager), if folder c:\test is selected in the left pane, it’s contents appear in the right pane. Now press a single down arrow key, and the left pane selection will change to c:\test1. A considerable delay occurs before the right pane refreshes. If the mouse is used, refresh is immediate. Why? and is this adjustable?