Windows 64-bit registry v.s. 32-bit registry

I ran into this issue not long ago. The short answer is that if you run a 32 bit application on a 64 bit machine then it's registry keys are located under a Wow6432Node.

For example, let's say you have an application that stores its registry information under:

HKEY_LOCAL_MACHINE\SOFTWARE\CompanyX

If you compile your application as a 64 bit binary and run it on a 64 bit machine then the registry keys are in the location above. However, if you compile your application as a 32 bit binary and run it on a 64 bit machine then your registry information is now located here:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\CompanyX

This means that if you run both the 32 bit and 64 bit versions of your application on the same machine then they will each be looking at a different set of registry keys.

Your understanding is correct. There wouldn't be any need for a x64 app to access the x86 CLSIDs since it could never load those components anyway and vice versa.

If you want to create component for use by both x86 and x64 then you need to either create a pair of dlls one built for x86 and the other for x64 and register both in their appropriate parts of the registry. The regsrv32.exe in the System32 folder will perversely register the x64 component and the regsrv32.exe in the SysWOW64 folder will register the x86 component.

Alternatively build a .NET assembly for Any CPU which can used by either CPU architecture.