I am running 64-bit Windows, and I want to create the registry key HKCU\\Software\\Classes\\Wow6432Node\\CLSID\\{myguid}\\InprocServer32 using C#.
HKCU\\Software\\Classes\\Wow6432Node\\CLSID\\{myguid}\\InprocServer32
What
Since you are targetting x86, simply using HKCU\Software\Classes\CLSID\{myguid}\InprocServer32 will work on all platforms.
HKCU\Software\Classes\CLSID\{myguid}\InprocServer32