Every key in the registry has a set of permissions saved to it that affects which users can read or write to it. You can see this in the Registry Editor by going to Run | regedit, right-clicking on a key, and selecting Permissions. WiX allows you to change these permissions with its PermissionEx element.
PermissionEx isn't in the default WiX namespace, but rather in WixUtilExtension. So, you'll need to add a reference in your project to WixUtilExtension, found in the WiX bin directory, and add the UtilExtension namespace to your Wix element. Here's the updated Wix element:
<Wixxmlns="http://schemas.microsoft.com/wix/2006/wi" xmlns:util="http://schemas.microsoft.com/wix/UtilExtension">
We've assigned the UtilExtension namespace to the prefix util. Now, when we create a registry key with a RegistryKey element, we'll nest a PermissionEx element inside it to set its permissions. The next example sets the permissions of a key called MyKey so that a user named nickramirez...