farooq473, replace the Inverter.
1) An LCD screen cannot produce enough light by itself. A Backlight is used to help provide the needed light.
2) An Inverter is used to provide power for the LCD screen, and the Backlight.
An Inverter boosts power up for the LCD screen, and lowers it for the Backlight.
90 percent of the time a bad Inverter is the problem.
A Backlight usually goes out all at once, Inverters slowly 'die'.
Dell Support > XPS 1210 Notebook PC > Service Manual,http://support.dell.com/support/edocs/systems/xpsM1210/en/SM/index.htm
In the list click on > Display
Now click on Display Panel.
Dell doesn't show, and describe how to replace the Inverter.
When you click on Display Panel, you are looking at an exploded photo showing the Display Panel removed.
Scroll down to the next small illustration.
Has 1, 2, 3, 4, and 5 pointing to the Display Panel.
5 shows you a pull tab to release a flat cable from the Inverter. The Inverter is the small circuit board to the left of the pull tab.
This is not advertising for this website. Just an example to show you what the Inverter circuit board looks like.
This is Not a Dell XPS 1210 Notebook PC. It is a guide for replacing an Inverter in a Dell Inspiron 1525 Notebook PC, but I wanted you to have photos, and instructions for the basic procedure.
After you have repaired over 100 laptops, you'll realize that they all have the same basic procedures.
Just different parts.http://www.insidemylaptop.com/replace-lcd-screen-inverter-dell-inspiron-1525-laptop/
3) Be SURE ALL power is removed from the laptop before you start.
Remove the AC adapter (Charger) and Battery.
4) You should follow Anti-Static Precautions implicitly. It would be best if you bought, and wore an ESD wrist strap. (Electro Static Discharge) Connect the alligator clip to a good ground source.
(For example, I connect to the metal frame of an empty desktop computer case)
The cost averages from $3 to $12.
A $3 ESD wrist strap will do just fine.
This is an example of an ESD wrist strap,http://www.amazon.com/Cables-Unlimited-ACC-1400-Static-Grounding/dp/B000EDMPQK
5) Use a multi-compartment container for the various screws you will remove.
Label each container for the area the screws came out of.
You DO NOT want to mix them up!
You can use a clean egg carton in a pinch. Label each egg holder.
Have questions post in a Comment.