allora... io ho fatto così:
codice:
Dim t As Long
Dim Wallpaper As String
Wallpaper = "C:\sfondo.html"
If Wallpaper = "" Then Exit Sub
t = SystemParametersInfo(ByVal 20, vbnostring, ByVal Wallpaper, &H1)
If t = 0 Then
    MousePointer = 0
    Exit Sub
End If
e in un modulo
codice:
Declare Function SystemParametersInfo Lib _
   "user32" Alias "SystemParametersInfoA" _
   (ByVal uAction As Long, ByVal uParam As Long, _
   lpvParam As Any, ByVal fuWinIni As Long) As Long
Lo sfondo me lo cancella, ma non mi mette come sfondo la pagina html. funziona con le bmp.