I think there is something else happening here.
Is the user logged on at the same time as the service? If so the registry hive could be locked. Are there any messages in the Windows event log?
The reason I think that the application should be able to access the HKEY_CURRENT_USER registry is because I tested this and created a sample C# Windows service (code below if interested).
Applications designed to be run as a service should however not store their information in a HKCU register hive. HKLM is the correct place for system wide application settings.
I created a new user account with administrative access under Windows 7. I then granted it Logon as Service rights, installed and started the service.
My findings were:
* When I ran the service, HKCU was loaded and able to be written to.
* When the hive was already loaded I got this message in the event log and the real hive was not updated. Instead a temporary hive was created.
Windows was unable to load the registry. This problem is often caused
by insufficient memory or insufficient security rights.
DETAIL - The process cannot access the file because it is being used
by another process. for C:\Users\OtherService\ntuser.dat
Also http://msdn.microsoft.com/en-us/library/ms684190(v=VS.85).aspx and here http://msdn.microsoft.com/en-us/library/ms684188(v=VS.85).aspx indicate that that even default system accounts do have a registry hive that gets loaded to HKCU, although it may be shared.
Code for test service
public partial class ExecuterSvc : ServiceBase
protected override void OnStart(string args)
protected override void OnStop()
public void TagRegistryHive(string KeyName, object Value)
// Load the hive.
var rk = RegistryKey.OpenBaseKey(RegistryHive.CurrentUser, RegistryView.Default);
catch (Exception e)