Keyboard Behaving Weird - Anyone could help

Hello,

Anyone can help to sort of this Issue for me.
I have Dell n5010 Laptop. Windows 7 6bit

Suddenly Some keys of my keyboard are inputting wrongly, same with spacebar and enter keys.

Ex: If I press backspace, it inputs [[[[[[yyyyyyyyyyy+++++++

I am not sure if this is an hardware problem as it is not happening always.

Remedies followed by me which were unsuccessful:

1. Tried re-installing my OS. After installing the OS for few days, I could not see this error. After few days, again same problem
2. I tried booting and working in Linux I mint, the same problem.
3. Changed the language options in the control panel.
4. I have a Mc-affee antivirus, also tried spybot and malwarebytes, junkfree etc.

Analysis on the problem my me:
I installed all the windows update - after that this problem occurred? I am not sure?
Once I used a different dell power adapter which was giving an error in the start-up screen "Your computer may behave abnormally" - I am not sure?


Anyone can help this issue, I don't have problem in changing the keyboard, but this problem should not occur thereafter, I am sure this is not hardware problem because, after re-installing my OS I did not see this error for more than 2 weeks.