Dell Inspiron 3537 Auto Scrolling

Hi

I have dell Inspiron 3542(service tag-97mkn52). my complain number is 937119095 and they have suggested to software support but it seems that its not an software problem.

From past few days, it is auto scrolling to bottom of the page. Even if I try to scroll up its taking me down.

This problem exists even outside OS. ie while trying to install OS.I have updated the drivers including bios setting in hope of getting the problem solved.I have also reinstalled the OS many time in hope but no use.Please help  me to know whats the matter.

In the keyboard no keys are stuck.I have also connected usb keyboard and mouse but it  make no difference.

I have done the all the test suggested by hardware support person and no error was reported.(both test was done).

Please help me.