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

64-bitclsidcomregistryx86

I heard on Windows x64 architecture, in order to support to run both x86 and x64 application, there is two separate/different sets of Windows registry — one for x86 application to access and the other for x64 application to access? For example, if a COM registers CLSID in the x86 set of registry, then x64 application will never be able to access the COM component by CLSID, because x86/x64 have different sets of registry?

So, my question is whether my understanding of the above sample is correct? I also want to get some more documents to learn this topic, about the two different sets of registry on x64 architecture. (I did some search, but not found any valuable information.)

Best Solution

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.