I tried various approaches tonight. Here is a very simple version:

    Function ThumbnailCallback() As Boolean
        Return False
    End Function

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim oImage As System.Drawing.Image
        oImage = System.Drawing.Image.FromFile("D:\MSN Messenger\20073.jpg")

        Dim objCallback As System.Drawing.Image.GetThumbnailImageAbort = New System.Drawing.Image.GetThumbnailImageAbort(AddressOf ThumbnailCallback)

        oImage = oImage.GetThumbnailImage(90, 100, objCallback, IntPtr.Zero)

        oImage.Save("d:\test.jpg")
        Exit Sub

Everytime the image is resized, it ends up in a format that is really weird. LView Pro can no longer recognize the file. I have to open with Windows Image Viewer. Isn't this supported in .NET?