I have an se w660i and i've bougt it from WIND. As i saw with the XS++ the only change that WIND has done is to set the shutdown graphic as custom stylized wind logo... so i deleted that (i wasn't at the ...system/settings..)
it was at the customization file (somewhere...:p) after the delete the phone was showing the stylized walkman logo at the turn off. Is this enough? or i must do sth more... the wap links the browser and everything else was not modified or generally bothered by the provider... only the shutdown logo...