Niaz,

Sorry I'm 'late'.

With an external display showing good graphics, with a laptop, this means the problem is the Video Cable,

(Display Panel Cable - HP), or inside the Display Assembly.

A small primer;

An LCD screen does not produce light,

http://solutions.3m.com/wps/portal/3M/en_US/NA_Optical/Systems/BehindTheScenes/Optics101/

(Click on monitor image)

It needs an additional light source.

A Backlight is the additional light source.

A Backlight can be a CCFL, (Or two of them), or a series of LED's.

(Light Emitting Diode)

The HP Pavilion nc6000 series of Notebook PC's, uses a single CCFL for a Backlight.

CCFL = Cold Cathode Fluorescent Lamp (Bulb)

Similar to Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.

Average thickness is 2mm. That is a little larger than 1/16th of an Inch.

Average length is almost as long, as the LCD screen is in height.

http://www.laptoprepair101.com/laptop/2007/12/09/replace-laptop-backlight-ccfl-lamp/

(View the last 8 photos)

A screen Inverter is used for CCFL backlighting. It is NOT used for LED backlighting.

A screen Inverter is used to convert the power, (Electricity), from the laptop; for the LCD screen, and Backlight.

90 PERCENT OF THE TIME the fault can be attributed to a bad screen Inverter.

Primer over.

HOWEVER, the other 10 percent of the time the fault can be attributed to;

1) Loose connection of the Video Cable To motherboard;

2) And/or loose connection of Video Cable TO back of LCD screen.

(Also connections of screen Inverter cables {Wires} should be checked )

Have personally found loose video cable connections, and have had users I have responded to through the years, also found loose video cable connections.

You HAVE to rule out that the Video Cable is not the problem first.

The Video Cable can also be damaged. If there is obvious signs of damage to the sheath of the Video Cable, chances are there will be damage to the tiny wires inside the Video Cable, also.

(Stretches/Broken)

A continuity test with a multimeter set to OHM's, should be performed for every wire in the Video Cable.

Perhaps there is a 'Mom and Pop' computer store nearby, that will perform this test for you, for very little charge.

Video Cable checks out the screen Inverter is next.

To check a screen Inverter requires a sensitive multimeter. Read fairly expensive,

http://www.fonerbooks.com/test.htm

Due to the low cost, and ease of accessing the screen Inverter, the choice to replace it may be the best option.

One example,

http://www.ebay.com/itm/For-HP-Compaq-nc6000-NC6120-nc8000-LCD-SCREEN-INVERTER-6038A0002301-LAPTOP-/280850639295

[The thin plastic frame in front of the LCD screen, is the Display Bezel. (HP) Behind it, and mounted towards the bottom of the LCD Screen Frame, is the screen Inverter ]

Screen Inverter test proves it's OK, or screen Inverter has been replaced; and internal display is still a problem; replace the LCD screen.

A) GENERAL pictorial example of replacing an LCD screen, and accessing motherboard connection of Video Cable; for HP Compaq nc6000 series of Notebook PC's.

Used to access the motherboard side connection of Video Cable, (Remove ALL power, remove Keyboard, remove Switch Cover),

http://www.insidemylaptop.com/remove-display-panel-hp-compaq-nc6320-nc6300-notebook/

B) HP Support > HP Compaq nc6000 series of Notebook PC's > Manuals > Service Manual > Download page,

http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?contentType=SupportManual&lang=en&cc=us&docIndexId=64179&taskId=101&prodTypeId=321957&prodSeriesId=367367#3

Service and maintenance information

Click on -

HP Compaq nc6000 Notebook PC - Maintenance and Service Guide ( 14 Jul 2006)

Regards,

joecoolvette