In order to change that:
- Open Windows Registry Editor
- Navigate to HKEY_CURRENT_USER\Software\Recisio\KaraFunPlayer2
- Find "CodePage" entry, and change it to whatever code suits your file (see below)
In most situations, 65001 will work, but if you need a specific character set, you can find a list of character sets and their associated code here: https://msdn.microsoft.com/en-us/library/windows/desktop/dd317756%28v=vs.85%29.aspx