Taskbar in XP Pro not showing running programs

> My taskbar at the bottom of my desk top works fine except
> I cannot see my programs that are running on the XP Pro
> taskbar. The only way to switch between programs is by
> using Ctrl/Alt/Delete. It works when I make a new user
> but I do not have all my programs and settings. What
> happened to cause this? I have another XP Pro machine.
> Is there something I can copy over using regedit to
> regain this ability? The quick start buttons and the
> Start menu on the left work fine. I just can't switch
> between running programs because they don't show up on
> the taskbar.
> Thanks and God Bless