Deepak Pathak sounds like a keyboard error if this happens in all programs etc. Replace the keyboard by downloading the service manual [https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjn2dmq55vOAhVn7YMKHWpBCmIQFggcMAA&url=ftp%3A%2F%2Fftp.dell.com%2FManuals%2Fall-products%2Fesuprt_laptop%2Fesuprt_inspiron_laptop%2Finspiron-15-intel-n5010_service%2520manual_en-us.pdf&usg=AFQjCNFwet7BmpbJKkF7-yatQTIZs2ZRNw&sig2=1WdcLN4Xg_UnoSCbar4GkQ&bvm=bv.128617741,d.amc&cad=rja|from here.] Page 28 will tell you what to do.