> AFAIK, the Win32_OperatingSystem caption is always ASCII. 

I think I was wrong here. The "Caption" field is localized, so the wmic.exe OEM encoded output to a pipe isn't reliable. The system OEM code page doesn't necessarily match the display/preferred language of the current user. It could be a lossy encoding with default and best-fit translations (e.g. "?"; "α" -> "a"). If using wmic.exe, it's better to redirect the output to a temp file, which will be UTF-16.