Thank you - in general this looks good. Two things I'd like to ask before a merge:

• was this code tests in a real setting with a remote attach? If not, could you please do it?
• the unittest looks sane - I assume it fails, if the remote registry service is not started - so if there is a separate error code, that indicates that, it might be worth checking for, if the error is unspecific, the test should be marked manual (See the SAFEARRAY tests, there is one I marked to be run only manually)

Hiya! Thanks for taking a look at the PR.

I just tested this on my localhost with the Remote Registry service started. It works as intended:

A user on StackOverflow also claimed (in a comment) that the mapping works.

As for the errors, it seems to return ERROR_BAD_NETPATH (0x35) if the remote service is disabled or if the path is just garbage. Doesn't seem to differentiate between the service being disabled and being unable to connect to the host. If attempting to use access a HKEY which is not one of the three supported ones, it returns ERROR_INVALID_HANDLE (0x6). I don't have an environment to test workgroup misconfigurations, lacking privileges or invalid credentials in, so I don't know which errors they might return. However, a Symantec support page I found suggests (in my opinion) that RegConnectRegistry may also return ACCESS_DENIED (0x5) if the user lacks privileges to the registry on the machine.

Should I make the test check for ERROR_BAD_NETPATH and leave a comment that it assumes remote registry is disabled?

Please adjust the unittest to check for ERROR_BAD_NETPATH and output a describing message to System.err, this way an interested party can see the result. This should not cause the unittest to fail.

Please also update CHANGES.md in the toplevel directory. You should add an entry to the features section for 5.0.0 describing your contribution. Have a look at the over entries and follow that pattern.

@cxcorp can I help you with the necessary changes?

Hiya, I made changes to the test, docs and CHANGES.md. Could you take a look?

Thank you - looks good and is merged to master.