[Alexfrey]

I am using windows 8.1 64-bit, i5, HP-pavilion laptop.

So, I have no idea how or when it started but i noticed that occasionally my single click leads to multiple instances of that application i.e if i click vlc once multiple instance of vlc are opened same with other software but this happens only some time so I did a malwarebytes scan, Windows MSRT scan but nothing came up, still  I restored my windows(formatted the c drive and reinstalled windows from my recovery partition ) i did not formatted the entire hard drive as i am not currently able to back up all the data (1tb) but after restoring windows there was no problem for like a month or so but the problem started again. 
one more thing when I switch on my laptop and it reaches the password screen it automatically behave as if someone is continuously pressing enter and shows incorrect password this loop continues until I press any other key. what is happening?

Malware bytes and other scans of avast and windows shows nothing.How should I proceed?

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Sounds like your keys are sticking.  You can check in Control panel, Keyboard that you haven't changed anything accidentally.  Looks like this on my Win 7:

 

[attachment=79538:keyboard.jpg]

 

You can try one of the many keyboard test available and see if they show anything funny:

 

http://www.passmark....cts/keytest.htm

 

seems to work OK.  (30 day free trial)  Don't worry if they don't have exactly your keyboard.

 

 

[RKinner]

Sounds like your keys are sticking.  You can check in Control panel, Keyboard that you haven't changed anything accidentally.  Looks like this on my Win 7:

 

[attachment=79538:keyboard.jpg]

 

You can try one of the many keyboard test available and see if they show anything funny:

 

http://www.passmark....cts/keytest.htm

 

seems to work OK.  (30 day free trial)  Don't worry if they don't have exactly your keyboard.

 

 

[Alexfrey]

my keyboard properties are same as mentioned above.

[RKinner]

Expect it's a flaky keyboard.  Can you stick a USB keyboard on it and see if that works better?

[Alexfrey]

Hey i ran your keyboard test it turned out that my numpad enter is automatically getting pressed so i would have to change the motherboard as they both are integrated!

thanks for your time.

Edited by Alexfrey, 13 December 2015 - 02:08 AM.

[RKinner]

Thought that might be the case.  

 

I've never seen a keyboard that was part of the motherboard.  What model number is the Pavilion?

 

As an alternative to replacing the keyboard it is sometimes possible to remap bad keys.  

 

https://sharpkeys.codeplex.com/

[Alexfrey]

I remapped the key but the same problem while booting, when it reaches the password screen it is behaving as if someone is continuously pressing enter.

[RKinner]

Expect the keyboard remap is not taking effect until after you log on.  I would go in to Control Panel, User Accounts and see if you can change it so it doesn't require a password so it bypasses that screen.

 

What model laptop is it?