These two APIs are very similar but it is unclear what the differences are and when each should be used (Except that LoadUserProfile is specified for use with CreateProcessAsUser which I am not using. I am simply impersonating for hive accesss).

LoadUserProfile http://msdn.microsoft.com/en-us/library/bb762281(VS.85).aspx

RegOpenCurrentUser http://msdn.microsoft.com/en-us/library/ms724894(VS.85).aspx

According to the Services & the Registry article: http://msdn.microsoft.com/en-us/library/ms685145(VS.85).aspx we should use RegOpenCurrentUser when impersonating.

But what does/should RegOpenCurrentUser do if the user profile is roaming - should it load it?

As far as I can tell from these docs, both APIs provide a handle to the HKEY_CURRENT_USER for the user the thread is impersonating. Therefore, they both "load" the hive i.e. lock it as a database file and give a handle to it for registry APIs.

It might seem that LoadUserProfile loads the user profile in the same way as the User does when he/she logs on, whereas RegOpenCurrentUser does not - is this correct? What is the fundamental difference (if any) in how these two APIs mount the hive?

What are the implications and differences (if any) between what happens IF

1. A user logs-on or logs-off while each of these impersonated handles is already in use?

2. A user is already logged-on when each matching close function (RegCloseKey and UnloadUserProfile) is called?