Why is the SetupDiCallClassInstaller function restricted to 64 bit programs?

Question

Attempting to call SetupDiCallClassInstaller from a program compiled in 32 bit mode fails on 64 bit Windows.

Apparently this is by design, but I\'d like to know the

Answer 1

If you are making that call from a 32bit process on a 64bit OS, it fails because it has to modify some registry keys in the 64bit portion of the registry. Where else if you were to make that call from a 64bit process on a 64bit OS, it would succeed likewise with 32bit process on a 32bit OS.