No Audio device !

Hey, i m using ACER-5735, window xp . suddenly, my sound system stop working. The error message comiing your sound device may not working properly but when i checked in control panel in volume tab in sound and device it is showing " No Audio Device ". My audio device manager is realtek. i checked the realtek hardward showing its location as well as the system is working properly.
my action: i uninstalled the said realtek sound device manager and re installed it , but no changed, the problem still persists with same message NO AUDIO DEVICE !

Please tell me the solution if u have !