Your code works for me, if my account is admin on the remote machine.

If the machine is operational, but I'm not an admin there, I get: 'error 0x80070005: "Access is denied"'.

This is different to your 'error 0x800706ba: "RPC "', which looks somewhat mutilated and probably originally was displayed as 'error 0x800706ba: "The RPC server is unavailable"'.

I got the latter message, if I try to access a non-existent machine.