Hi nandyalas,
I suggest you to run MS Fix It to fix the issue: http://bit.ly/JvQScV
If the problem persists, please Run PC Diagnostics on sound card from the link: http://dell.to/120qdSZ
Also please reply with the system model and operating system, for further help.
To know more about Dell’s products, services and drivers & downloads, please go to http://dell.to/YBlak6
Awaiting your response.