beginner Q: Vista registry permission

By default, my software cannot write to HKU\.Default\software\mykey\

The RequiredExecutionLevel is set to user. I'm using the AccessControl plug-in to set the permission on the HKU key as 'Everyone' (ideally) but i've also tried (BU).

Problem:
It has worked a few times, but fails most of the times. However, if I change the RequiredExecutionLevel to admin. Everything works fine. My software can write to HKU.

Is there a way to set permission on HKU using NSIS installer without setting the RequiredExecutionLevel to admin?
Sorry for making a few posts on the forum, i'm trying to learn this great installer.

No, you need admin rights to change .Default, no way around this. If you want to setup some kind of default config for your app, its better if your app detects that HKCU\software\yourapp is empty and reads its default config from its installdir or hardcode the defaults in your app

Thanks Anders. With the elevated permission ('admin'). It works fine all time. It's strange that the AccessControl plug-in still works at times even when the installer is set to 'user'.
I appreciate your reply!