Iam using ubuntu 9.04.sound card is not working.I

If you are getting sound through your speakers then the sound system is working. If you lose the sound when using the headphone jack then either the headphone jack is faulty or your headphones are...

Although, rarely, you may find that opening the alsamixer from the terminal will fix the problem as some versions of Ubuntu have a special volume control for the headphone jack....

You will need to open the mixer as the Administrator
Type
su aslamixer

If this helped please vote kindly