The other day I was trying to install Windows XP SP2 on a computer that had SP1 installed. I’m not sure how it got to SP1 (upgrade from XP, upgrade from Win98, etc), but I kept getting to a certain point that was telling me “Access Denied”. As I researched this it turns out it was a permissions error in the registry. The suggested answer was to reset permissions on 4 registry keys, but as I looked around the registry, there were all sorts of permissions that were wrong. I’m not sure what happened, but I did figure out how to reset the permissions back the default.
“Access Denied” error when trying to install SP2
This article explained how to use the SubInACL utility from Microsoft to set the permissions on certain registry hives. I guess this doesn’t specifically set them back to the default, but it allows you to set hives or keys to what you want the permissions to be.
How to reset security settings back to the defaults
This Microsoft Knowledgebase article does explain how to reset the permission to the default. It uses a utility that is included with Windows XP so it is very easy to use.
Remember, this tip isn’t just in case SP2 won’t install. If you have been messing around with the registry and changed permissions, this is a way to get them back to the default. And of course remember… when you are working with the registry, be sure you have a backup in case you do something wrong.