That only works if characters in filenames can be represented by the codepage. All other characters are replaced by question mark. Basically, this code from win32.c:

WideCharToMultiByte(CP_ACP, WC_NO_BEST_FIT_CHARS,                     
+                wFindData.cFileName ... )
[download]

does the conversion, and CP_ACP is (qoute from MSDN) "the current system Windows ANSI code page".