How Install the Nvidia driver in Unbuntu Lenova T520?

Recently I required to change my hard disk to a new lenova machine. I'm using ubuntu. And every thing works well after I change the hard disk, but I had a problem with my screen resolution. It was set to 4:3 and that was the maximum resolution available. It was really hard for me to work with that less resolution.

And found the reason was the driver for my display, Nvidia is not detected correctly so that I installed the Nvidia driver again in my Ubuntu machine.

The following are the steps I followed to install the Nvidia driver in my machine.

1. sudo add-apt-repository ppa:ubuntu-x-swat/x-updates 

2. sudo apt-get update

3. sudo apt-get install nvidia-current 

After installing the driver, I restarted the machine and changed the resolution (Applications -> System Tools -> System Settings -> Displays) to 16:9, and solved the resolution problem :-)