Midi playback solved thus

Thanks all for yr help. Blundering about I went thus:-

Settings> Control Panel> Sounds & Audi Devices Properties> Midi Music Playback> cascade down to MS GS Wavetable SW Synth> Apply

On clicking on a Midi file I was prompted to choose a playback prog so I highlighted WMP and put a checktick in the box to "always use that file" --- and job done.