using (FileStream fs = File.Create(@"myfloppy.vfd"))
{
    using (FatFileSystem floppy = FatFileSystem.FormatFloppy(fs, FloppyDiskType.HighDensity, "MY FLOPPY  "))
    {
        using (Stream s = floppy.OpenFile("foo.txt", FileMode.Create))
        {
            // Use stream...
        }
    }
}