Hi Folks , I've sorted the problem !!
Everything is now ok !!
I had the Mixer Lock activated !!
(highlighted in black) on the right hand bottom of the screen .
I tried reading the manual on the mixer lock function (it's not exactly easily understood )
Anyhow, if the mixer lock is set in the on position , and you switch the Xp off .
On start up you setting returns to default
settings of 127 volume level .
So it's something else I've learn't .

Regards to you all..........Giovanni