In my case it was caused by what I had done and here is what I did to correct it.

 

 In my case this was caused by me moving things around in the documents and settings.  My documents and settings has the following folders

 Administrator
 J
 All users
 Default user
 Localservice
 Networkservice

 I had moved all my startup to all users and removed the startup folders from C:\Documents and Settings\j\Start Menu\Programs\ and from C:\Documents and
 Settings\default user\Start Menu\Programs\Startup
 This was a mistake because I had moved my Lexmark printer programs to startup in all users as well as zone alarm.
 Windows xp then did me a big favor and changing the following keys.

 HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\
 User Shell Folders\Start up

 %all users%\Start Menu\Programs\Startup

 Which was the same as the following key.

 HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\ShellFolder\Start up

 This loaded the printer and zone alarm twice once at location startup and once under common startup I did the following to correct.

 I went to windows explorer and made sure I had a startup folder under
 C:\Documents and Settings\default user\Start
 Menu\Programs\ if you do not have it make a startup folder there.

 I then went to start the run and typed regedit, and then went to this key

 HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\
 User Shell Folders\Start up
 I then right clicked on startup and pick modify and change just the all users to default user.

 %all users User%\Start Menu\Programs\Startup was changed to
 %Default User%\Start Menu\Programs\Startup

 Then I restarted my computer and only had the common startup location for the programs.
 

You're a  LIFESAVER!  I did what you suggested and it did the trick.

It turns out that I must have caused my own problem by trying to move the Startup folder from my own account to the All Users one.  What must have caused the problem was the deletion of the Startup folder from my own account folder.  That must have changed the registry key.

Anyway, I went into the registry to the key

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders\Start up

and changed the value from

 %ALLUSERSPROFILE%\Start Menu\Programs\Startup

to
 
 %USERPROFILE%\Start Menu\Programs\Startup

you do not know how many months I worked on this problem before I got it fixed and I saved a copy just so I could help someone else if they needed it.  Not a easy thing to fix.