Dear Brightguy,
I tried both methods. None helped.
But paying more attention I noticed that when in the Device Setup panel there's no device defined for MIDI (no Midi) a dialog box appears saying: "MMSYSTEM05 The pointer of the identificated device is invalid" (that was translated from portoguese). When I choose a device in the panel, the program crashes as soon the play button is pressed (illegal operation performed). Formerly, from that point, the program crashed no matter the file type to be played but now, after restart, it's playing wav and mp3 files normally....
It's not so important to play MIDI with xmplay but, since it's possible, I want to have the option active. But the program must MIDI through Wingroove and/or use the Winamp .sf2 support.
Is there a vampire in my system...

...hehehe....
C'mon Brightguy, I need your light....!!!!
Carlos