DNS server not connected message

Hi !!

Since two weeks my windows-7 computer is showing error in connection but I am connected to the internet. When i tried to troubleshoot the issue i got a warning that DNS server is not responding. But the internet connection exists. As data transfer rate is changing and also the firefox is running. Problem is for the internet explorer & utorrent...I alos tried restoring the computer to all the previous dates but still problem exits.

Can somebody help me...

Thank you.