Unable to install some updates

I've been unable to install the following updates to my
windows 2000 professional SP4 loaded computer:

Security Update for Windows 2000 (KB840315)
Security Update for Windows 2000 (KB842526)
Security Update for Windows 2000 (KB841873)
Security Update for Windows 2000 (KB841872)
Security Update for DirectX 9.0 (KB839643)
Security Update for Windows 2000 (KB839645)

and the following Recommended update:

Update for Windows Media Player 9 Series (KB837272)

from the windows update site:

http://v4.windowsupdate.microsoft.com/en/default.asp

All other updates install correctly, but when I try to
install the above referenced updates, I get an install
failure message from the web page and after downloading
and trying to install the updates manually, I get the
following message:

Setup Error

You do not have permission to update Windows 2000. Pleas
contact your system administrator. I could understand
this, but I AM the system administrator.

I attempted the fixes specified in Microsoft Knowledge
Base Articles 316524 - "Administrators only" error message
when you attempt to use Windows Update Site and
326686 "Windows update was disabled by your system
administrator" error message, with no success.

Are there any other steps I can take save flattening and
reinstalling the image?