Dell Inspiron N5110 :: Reduced Performance In Gaming And Watching Streaming Videos

I have a Dell Inspiron N5110.  After two years, my laptop starts to have reduced performance in gaming and watching streaming videos. I did a factory reset. Everything seems fine. 

I did a test by installing Warcraft 3 which I played with no lag at all. After that, I started to install/ update the Graphic drivers, Windows updates and installed Starcraft 2.

Then I played Warcraft 3 to test the performance and it lags like for every 2 seconds in game. 

Please note that I test my system by playing WC3 after installing the following individual items:

Item 1: Graphics driver
Item 2: Windows updates
Item 3: Starcraft 2 

Please note that I did three (3) factory resets.

This means I install WC3 and played and there is no lags. When i do Item 1, WC3 lags. 

This means I install WC3 and played and there is no lags. When i do Item 2, WC3 lags. 

This means I install WC3 and played and there is no lags. When i do Item 3, WC3 lags. 

  Please note that I did a hardware diagnostic test and I pass all the tests. 

I also did played around with: 

1) Power Settings 
2) Nvidia Control Settings and used the my graphic card instead of integrated video card.

But I am still facing the lag. 

At the moment, I am using my laptop at the factory settings and not installing any drivers or updates.