You could try to take a look at the package Core. It has a file called CharSet.h. This file has a bunch of UTF-8 related functions. You can start from ToUnicode() or ToCharset().
when i use some core function,
For example, GetExeFilePath();
i got a string like this"F:\game\²âÊÔ.exe";
Got where? What means are you using to display this string and on what platform.
All filenames get converted to the encoding of your application, which by default is UTF-8. And if you use GUI functions (like PromptOK), it should display correctly as well.