[DllImport("winmm.dll")]
private static extern int waveOutSetVolume(IntPtr hwo, uint dwVolume);
private void SetVolume(int volume)
{
int NewVolume = ((ushort.MaxValue / 10) * volume);
uint NewVolumeAllChannels = ((Convert.ToUInt32(NewVolume) & 0xffff) | (Convert.ToUInt32(NewVolume) << 16));
waveOutSetVolume(IntPtr.Zero, NewVolumeAllChannels);
}