In the Save As dialog, the left side should be organized into two sections:
Favorite Links and Folders. If Folders is collapsed and sitting at the
bottom, click on it so you can see your folders. You should be able to use
that structure to navigate to the folder of interest.
If you put the mouse pointer over the top edge of the line that says
Folders, you can drag the Favorite Links/Folders divider so that you can
control how much of each you display. Note that the whole Save As dialog can
be made larger by dragging any of the sides or corners.
If you see only one large pane, by the way, rather than left and right, then
on the toolbar, click Organize - Layout - Navigation Pane.
One you have the target folder in your sights, you can drag it to the
Favorite Links area to put a shortcut to it there. That way, the next time
you need to access that folder, you won't have to navigate to it.
Note that the Save As and other file dialogs in Word 2007 are special
versions of Windows Explorer. Any links you create in Word or other Office
programs will be available in Windows Explorer also, as well as in any other
applications that use this facility for displaying files.