Windows explorer right pane doesn't show the entire C: drive
 

My windows explorer default is set to show my C: drive expanded. In
the left pane, the entire drive contents shows - in the right pane,
the listing starts with "documents and settings"; the first third or
so of folders on the drive aren't listed, the rest show normally. This
is happening whether the view is set to icons or list (Mine defaults
to list). The sub folders open normally when clicked on in the left
pane. This started happening about a month ago - prior to that all of
drive C: contents showed in both panes. Anyone have any idea what
caused this and what I can do to fix it? I'm using a Gateway laptop,
running XP Home, fully updated, SP3 except for internet explorer (ver
6) which I don't use. I'm using Firefox, version 3.5.7

Thanks in advance - Bob