Those registry entries look fine too, like in winner's case on Win7. Are the files shown as "XMPlay-able" in Explorer, and does double-clicking on them result in them being opened with XMPlay? For some further info, please also export and upload these registry branches...
HKEY_CURRENT_USER\Software\Classes\XMPlay
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.mp3