DwmIsCompositionEnabled

C# Signature:

[DllImport("dwmapi.dll")]
private static extern int DwmIsCompositionEnabled(out bool enabled);

VB.NET Signature:

<DllImport("dwmapi.dll")> _
Private Shared Function DwmIsCompositionEnabled(ByRef enabled As Boolean) As Integer
End Function

Notes:

Public Function AeroEnabled() As Boolean
     If Environment.OSVersion.Version.Major < 6 Then Return False
     Dim Enabled As Boolean
     DwmIsCompositionEnabled(Enabled)
     Return Enabled
End Function

Notes:

Public Function AeroEnabled() As Boolean
     If Environment.OSVersion.Version.Major < 6 Then Return False
     DwmIsCompositionEnabled(AeroEnabled)
End Function

If you're using DevExpress components::

DevExpress.Utils.Drawing.Helpers.NativeVista.IsCompositionEnabled();