Hi,
You can use a COM Windows Media Player control in a Windows Form application :
axWindowsMediaPlayer1.URL = @"D:\Data\krishna.wmv";
axWindowsMediaPlayer1.settings.rate=2.3;
axWindowsMediaPlayer1.Ctlcontrols.play();
Here "rate" is used to set speed of the video. Default value is 1 which is normal.
To slow down its speed set "rate" to less than 1 but greater than 0 like 0.2, 0.4 etc.
To speed up set "rate" to greater than 1