XP Service Pack 3 installation failed

This has happened twice--once yesterday, once today. Each time I click to download and install SP3 from the Microsoft Updates website, I get a message that it has already been downloaded and partially installed. It says to click to continue installing. I do, and eventually I get the "failed" message. The error code is: Error Code: 0x80070005. Every time I try to use MS help, I run into difficulty. Can someone help me? Thanks.

 

You have problem with Windows validation tool.
This issue is related by the WGADiag2.exe tool. I also suggest
using the WGA diagnostic tool to check the issue

1. Please open Internet Explorer and visit the following link to download
the WGA Diagnostic Tool:
http://go.microsoft.com/fwlink/?linkid=52012
2. Save the WGADiag2.exe file to Desktop, and then double click on the file
to run the tool.
After running the tool, please return to Windows Update and see if the issue
is resolved.

 

Thanks. I did what you suggested, but it did not solve the problem. This time, I sat at the computer and watched the lengthy process. At one point, the window was labeled "The Updates Are Being Installed." Below that was "Installation Status" and it said: "Initializing installation...done" and "Installing Windows XP Service Pack 3 K3936929 (Update 1 of 1)..." Suddenly, the following box showed up: "Service Pack 3 Setup....Access is denied" with an "OK" box inside. I clicked the OK box and got another box: "SP3 Setup Error: SP3 installation did not complete. Select OK to undo the changes that have been made." Instead of clicking the OK box, I immediately went to this thread and wrote out this reply. (I had to go to another browser to do this because IE wouldn't let me do anything but click the OK box.)

 

Try this:http://www.windowsreference.com/win...sp3-install-fails-with-error-code-0x80070005/

Look at this site why:http://forums.techarena.in/windows-update/1009694.htm

 

Thank you for your efforts. I checked the registry and did not find anything amiss. I disabled all my anti-virus, anti-malware programs and SP3 still would not install. I checked out SubInACL that was referenced in one of the links you listed, and it scared me because I'm not that advanced with computers. Do you think I would run any serious risks if I just forgot the whole SP3 thing?