Dear Asad,
I had same issue when i degraded my Dell Inspiron N5050 from DELL Ultimate OEM Win 7 to Dell OEM Home Basic Win 7 today morning..
I ve gone crazy coz of the erratic nature of my mousepad..and i have searched so many forums and found some having same issues..
but my search for the solution was in vain..
Please remove any other chargers of phones or tablets like samsung, blackberry, or iphone, which is connected in the same wall socket using adaptors or another socket in the same room.
it will be fine..if it still doesnt work call an electrician and check your Earth line in the main power supply line.
Regards
Jake...