you first must have total commander:
http://www.ghisler.com/pocketpc.htm
EDIT the "26948339_manila" file under windows and look for :
<Page Order="4" Name="music.page" PackageName="HTC" Title="[[IDS_MUSICTITLE]]" ExternalScriptPath="HTC\Scripts\sprintmusic.luac">
<ComponentReference Name="page" Mode9Path="HTC\music.mode9" Component="GizmoRoot" SmartComponent="true" />
<ComponentReference Name="icon_normal" Mode9Path="HTC\icons.mode9" Component="Music_Off" />
<ComponentReference Name="icon_selected" Mode9Path="HTC\icons.mode9" Component="Music_On" />
<ComponentReference Name="icon_preview" Mode9Path="HTC\icons.mode9" Component="Music_Preview" />
</Page>
Then REMOVE:
ExternalScriptPath="HTC\Scripts\sprintmusic.luac"
soft reset your phone and that sprint music store banner should be gone!