Thank you for your reply. My seriatim reply is as follows:

  • I don’t think problem is related to Avast! as it was working all right upto 3rd Sept.
  • I am using Vista Home Premium and it is uptodate.
  • I am running Avast 4.7 Home.
  • Configure microphone but it says it didn’t detect the microphone.
  • I don’t think any other security program is interfering. It was working up 3rd Sept, and on 4th Sept I see an optional update for Intel Graphic Chipset from Microsoft. I am not sure but it stopped working when I tried to do voice chat on 5th Sept. On 4th I didn’t try for voice chat. So I am not sure if the update on 4th Sept is the cause.
  • Control Panel > Administrative Tools > Events, specially ‘Errors’. I see number of errors but I don’t understand much what they are but as I feel there is none relating to microphone.