Registry Redirection for 32-bit applications on 64-bit OS

Well, this title looks complicated...actually the story is pretty simple by using an example.

For example, you write an application APP_A and the installer of this application needs to leave fingerprint on system's registry keys, so that the other applications/users can know APP_A is installed on the system. Assuming that "fingerprint" is "HKLM\Software\Microsoft\App_A", and you selected the target platform as "Any CPU" when you build it, it looks like that you are done. However, if your APP_A is installed on 64-bit OS, the other 32-bit application will complain that it can not detect APP_A.

Why? Simply because registry REDIRECTION. Because here HKEY_LOCAL_MACHINE\Software is redirected to HKEY_LOCAL_MACHINE\Software\Wow6432Node.[However, please note that HKEY_CURRENT_USER has no redirection here].

Therefore, if your application wants to support the access of those 32-bit applications/processes on 64-bit OS, you need to leave fingerprints on both WoW6432Node and regular node of HKLM registry key. About registry redirection, more information is at https://msdn.microsoft.com/en-us/library/aa384232(VS.85).aspx

[PS: how do you know the application is 32-bit or 64-bit? Use "dumpbin", a command line tool. for example, on 64-bit OS, %windir%\syswow64\cmd.exe is a 32-bit command shell and %windir%\system32\cmd.exe is the 64-bit command shell (the default one on the start menu)]

Comments

• Anonymous
  August 11, 2010
  Hi, I've to install Win732 bit os as well as 64 bit using single winpe (32 bit winpe). I'm able to do that. Once installation is done, I need to register for autologon once. I think, as winpe is 32 bit, it is updating the autologon details in Wow6432 node. and because of this Auto logon is not happening. Do you have any solution for this.??

• Anonymous
  June 07, 2011
  I have the same problem. In 64bit windows when I wan to update autologon information foe a specific account, it'll be redirected to Wow6432Node. Any idea please ?