When installing Microsoft XP SP3 many users have reported errors due to permission problems in the Windows registry which then causes the service pack to fail.

Windows Registry permission problems are often caused by anti-virus software, or connecting / disconnecting from different domains(network environment).

Error messages include:

• Service Pack 3 setup error. Access is denied.
• Service Pack 3 setup error. Service Pack installation did not complete
• DoRegistryUpdates failed
• Various permission errors

There is a simple fix for this problem. Detailed below

 Option 1 (automatic)

1. Download and Install the SubinACL tool from microsoft.
2. Download and run the attached file - reset.cmd  (attached to the bottom of this article)
3. The reset tool may take some time to process your registry - so leave it running
4. When complete the tool will exit

At this point you should be good to go - to reattempt XPSP3 install.

Note: Run these tools as administrator.