Automatically types letter E.

I have a dell vostro 14 laptop. I have came across a problem that when ever I use my laptop the letter e automatically types.. I changed the keyboard multiple times but no result. The problem occurs even after disconnecting the keyboard from the laptop.

The problem also occurs in bios and in command prompt windows. I changed my os number of times, removed battery, changed hdd but nothing is helping me out.. I contacted the local dell service center but they were unable to help me out.

If anyone have solved such an issue please help me out.