“Access denied” error when installing service pack

I’d expect demand for solutions to Windows XP service packs installation issues decline by now… But according to stats on my failed to install catalog files post it only increased lately.

Among numerous comments on that post e.r.lehmann had mentioned that service pack installs can also fail due to registry issues. Took some time but this week I encountered exactly that – service pack failing with Access denied error.


Service pack 3 installation seemed to proceed as normal up until almost end. Then it threw “Access denied” error and rolled back installation.


Error itself doesn’t specify access to what exactly is denied. You can locate and look through svcpack.log file in Windows directory for specifics.

Anyway it seems that this error in this context is almost exclusively refers to Windows registry access. Service pack naturally has to make numerous registry changes during installation and without that it can’t complete.

Microsoft support has article on issue - When you try to install Windows XP Service Pack, you receive the error message “Access is denied” or “Service Pack installation did not complete”.

Steps to fix

  1. Check computer for malware.
  2. Verify that you launch service pack installation under account that has administrative privileges.
  3. Stop and/or exit security software such as firewalls and antiviruses. For some products that may not be enough and manual stopping of background services or even uninstallation will be required.
  4. If steps above have no effect – reset registry permissions, using SubInACL and secedit; support article has exact script you should use.

In my case it took all these steps to resolve the issue. Command line fix was kinda scary – it threw a lot of errors and last step took long time (over ten minutes). Despite that after it ran service pack installed just fine.


When everything is fine any administrator account should have sufficient privileges for service pack installation. However because of security software (and virus infections I suspect) registry access rights can become considerably broken.

Determining and removing likely software/malware culprits and resetting access permissions should be sufficient to resolve issue in most cases.

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  • kelltic #

    I have to wonder why this should be so difficult. If it was scary for you, imagine a know-nothing like me trying to follow MS's instructions. I postponed installing Service pack 3 until the last minute. Well, until June 12th. If it failed, and I was afraid it would, I'd have had to decide whether to just stick with SP2 or run off to the tech's place for a fix. Congrats on completing your diploma project on programming courses. Yes, you still have readers.
  • Rarst #

    @kelltic Well, I will protect Microsoft here a bit. This particular PC was veeeeeery screwed up - tons of wares, malware and whatever. And even if SP3 was not installing it was also rolling back correctly and not breaking further system that was barely functional already. Ok, enough with protecting Microsoft - I hate Windows registry so much! :) Thanks and glad to have you!