On switching on my laptop dell latitude D630, the screen does not display even i can't see any process on the screen. What can be the possible cause?

Did you mean a conversion to an external monitor or do you mean on the same machine؟

Hi, if the power light is glowing, and the display is black, the root causes might be the RAM or Hardware issue with the display or the harddrive itself, We need to diagonise futher by researting RAM and Harddrive. And many more work arounds.

RAM or Motherboard may be damaged 

• The possibility that the video chipset has failed but normally, you would also see problems with the external display as well - for example, loss of ability to output at the monitor's native resolution (assuming that the monitor isn't capable of an output that exceeds the video chipset's capabilities), video corruption, strange colours on screen, etc...

If the device is equipped either a VGA or DVI Port, Better to connect it to a different screen, just to isolate the the problem of it's an LCD Problem or a Motherboard Issue

If after turning on a light indicator for ON display but no Displays on the screen.. It could be one of the following

- Bad of failing RAM

- Bad or Defective Display Chips on the Motherboard

- Bad Capacitors on the DC Power Circuit inside the Laptop

- Defective Flex Ribbon

• Did you mean a conversion to an external monitor

if the monitor turns on,but it is not display anything on the screen means RAM problem.(RAM failed).

if you can turn ON the laptop,the light indications are run on the keyboard,but monitor didn't turn ON

means display problem.

you have to check the VGA port by connecting it to external screen if u see the picture then the problem is laptop's LCD screen ( inverter board or flat cable ...etc) but if u didnt get the image on external screen then the possible problem is Graphics chipset on motherboard , some Dell laptops has detachable VGA/Graphics card so u can change it easily

On the same machine

it's a screen problem and you have to check it with an external display