COM activation change in Windows Vista
In Windows Vista, COM will read HKLM\Software\Classes when the process has a integrity level > MEDIUM, and it will read the merged HKLM\HKCU hive otherwise.
For information about integrity level, please read Steve Riley's article Mandatory Integrity Control in Windows Vista.
This means, for services running at system context, or elevated applications, COM will only read HKLM\Software\Classes.
