Error: 0X51F, SP3, Office 2003, XP

I do not have disk, Office 2003 came with my computer when I bought it.
Running XP. Office 2003 SP3 will download but not install. Previous SP1 and
SP2 installed OK. Numerous attempts to install SP3 have failed. Why can't
Microsoft adjust download-updates to install properly? Need detailed
instructions in simple language in simple steps to get this to install.
Thanks in advance for any possible help.
--
Norske

Tip: See if you can download the "fullfile" version of the update(s) via
http://www.microsoft.com/downloads/ or http://catalog.update.microsoft.com/
and then install it/them manually.

Has KB949074 been installed?...

Description of the update for Office 2003 (December 9, 2008)
http://support.microsoft.com/kb/949074

Also see...

You cannot install an Office 2003 service pack
http://support.microsoft.com/kb/884298


Norske wrote:
> I do not have disk, Office 2003 came with my computer when I bought it.
> Running XP. Office 2003 SP3 will download but not install. Previous SP1
> and
> SP2 installed OK. Numerous attempts to install SP3 have failed. Why can't
> Microsoft adjust download-updates to install properly? Need detailed
> instructions in simple language in simple steps to get this to install.
> Thanks in advance for any possible help.