how will i fix this problem?

Could be a problem with the screen itself or, less likely, a fault with the video card.

Try upgrading your video drivers. It can't hurt and have a slim possibility that it may resolve your problem.

Try connecting some external display. If the lines are still there, the video part of the motherboard is faulty. On a laptop, it can't be fixed. You need a new laptop.
On a desktop model, you'd need to replace the video card.

If there are no lines on the external display, your screen is faulty and need to be replaced.

Electro
July 2013