It looks like the exported file is utf-16 (at least that's what gives me legible results when I open it using that encoding), but apparently RegSetValueEx wants a utf-8 encoded string?

How to Convert a File From ANSI to UTF8. ANSI and UTF-8 are two types of text encoding. The former is the default encoding that is used when you save text files created in Notepad, the text editor ...

Notepad Encoding Options Different software programs encode characters in different ways. Notepad can manage text encoded in several formats such as ANSI, Unicode and UTF-8.