Structure of Registry: HKCR vs. HKLM; Wow6432Node branch

[pstein]

I have some questions about the structure and dependencies of Registry branches.

When I inspect (on 64bit Win 7) all entries of a certain program then I found two identical branches of it in

HKEY_CLASSES_ROOT\

and

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\

Is the second a replication of the first?
In other words: If the second is not existing: Does it automatically acces the first as a kind of fallback information?

Similarly I found identical branches in

HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\

and

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Clients\Mail\

Here the same question arises:
Is the second a mirror of the first?

What if they contradict each other: Which one has priority?

Peter

 

[Lance1]

This should answer your question. How the Windows Registry Works

 

[LMiller7]

The HKEY_CLASSES_ROOT key is just a link to HKEY_LOCAL_MACHINE\SOFTWARE\Classes. It is a different way to look at the same data. There are other examples of this in the registry.

The HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node subkey exists only in a 64 bit OS. It is used by 32 bit processes and when they attempt to access HKEY_LOCAL_MACHINE\SOFTWARE they will be redirected to HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node. While the contents may appear identical, and some subkeys may be, they are not the same. This is necessary when both 32 and 64 bit versions of the same application are installed. It is really a lot more complicated but that is the basic idea.

The file system and registry structure in a 64 bit OS has been criticized as being overly complicated and at first examination appears to make no sense. Even experienced developers who should know better have done this. But there are good and valid reasons for things being as they are, even if they are difficult to understand. I will not attempt to explain them here.