Since you have graphics on an external monitor, the problem is the Video Cable, or inside the Display Assembly.http://h10025.www1.hp.com/ewfrf/wc/product?product=3860431&lc=en&cc=us&dlc=en&lang=en&cc=us
This is a general example of a Video Cable, (Display Cable - HP), for an HP Pavilion DV4 series of Notebook PC,http://www.ebay.com/itm/NEW-ORIGINAL-HP-PAVILION-DV4-LAPTOP-LCD-VIDEO-CABLE-DC02000IO00-486878-001-14-1-/281038275215?pt=US_Laptop_Screens_LCD_Panels&hash=item416f2fc28f
Mouse over to enlarge
The Video Cable connects to the motherboard in an area under the Keyboard, (About where the Fn key is), routes up along the motherboard, then routes up through the left Hinge, and into the Display Assembly.
From there it connects to the screen Inverter (Display Inverter -HP), and back of LCD screen.
It also connects to the LED backlight.
Either connections are loose, or the Video Cable (Display Cable) is damaged.
If the sheath of the cable shows apparent visual damage, so may be the tiny wires inside. (Stretched/Broken)
Connections CANNOT just be visually determined if they are loose.
You MUST physically check EACH connection.
Tightening connections does no good?
Perform a continuity test with a multimeter set to OHM's, on every wire in that Video Cable.
Have an assistant gently wiggle the cable in the middle, and check for an intermittent reading on the multimeter. Indicates broken wire if intermittent reading shows.
Take Video Cable to the nearest small computer store, and have the resident tech check it for continuity. Should just be a couple of bucks.
Use an ESD wrist strap, and connect it's alligator clip to a good ground source. (Electro Static Discharge)
Average cost is around $3 to $6.
Here is the download page for the free Service Manual, from HP Support,http://h10025.www1.hp.com/ewfrf/wc/manualCategory?cc=us&dlc=en&lang=en&lc=en&product=3860431&
Scroll down, click on -
HP Pavilion dv4 Entertainment PC - Maintenance and Service Guide
Page 92 (PDF page at Top) for motherboard side of Video Cable (Display Cable - HP)
Page 80 for LCD screen, and Screen Inverter (Display Inverter - HP), and LED backlight.
Page 82 has false statements.
Remove the display assembly:
1. Locate the wireless antenna cable (1), and remove from path (2)
Locate the DISPLAY CABLE (1), and remove from path (2)
2. Disconnect the wireless antenna cable from the system board (3)
2. Disconnect the DISPLAY CABLE from the system board (3)
Somebody was on crack that day.
The wireless antenna cable information that follows, is correct.
Video Cable (Display Cable) is on the Left side.
Wireless Antenna wires are on the Right side.
For additional questions please post in a Comment.