All leds are light on or glow but the screen display is always black and no display but the fan and hard drive are working and spinning

Try to hook to a secondary display.

It would be helpful if we knew the Make, Model of Laptop and the OS you are using? Try a hard restart , remove ALL media, DVD, CD, USB, etc., unplug , remove battery, leave battery out, plug in , reboot. Describe what happens, Fan spins? LED's blink? HDD spins up? Sound? Anything on screen? Have you tried a System Restore/Recovery? You can start by removing the HDD and testing it, if you done have a USB to sata/ide adapter take it to a Qualified Computer Tech.

When this happened was the laptop overly hot? If the laptop's head got too high it could have shutdown to protect itself. It wouldn't boot until the heat had disparate. Sit you laptop aside for about 30 minutes and see if it will boot then. If it does you might want to check out a cool mat.


http://www.amazon.com/gp/product/B008TO35G0/ref=sr_1_3?ie=UTF8&qid=1358444754&s=pc&sr=1-3

Hey and old DV4 that still glows with those bad CCFLs lamps.
a hark moment wow look at that baby run and should not.
not now.
the cpu never ever fails, why do that?
what matters is , my short list the a link for 10 to 20 causes.
ok>
first is the fan, it must spin and blow and the Radiator and vents inside must not be packed in lint as all are this old ,<hint
got flash codes, bore beep post codes.
the Caps look LED will show blink codes, if there are POST errors
does it?
take out the old relic and shorted main battery. and run on AC for even for ever. does not run now.
does the screen show text as it must booted.
oh oh, its 2008, 10 years old and guess what 2008 is the year
of what, bad Nvida chips, called the solderballs from, H3LL.

1: fans dead?
2: main battery out. ! the BIG-EN"
3: NEW COIN CELL. if its dead so be BIOS and time of day
4: screen dead, never ever ever show text or logos.
the "Hit F10 to enter setup" seen for 10 years now is missing right?
5: a real monitor (Fn+f4 keyed up) connected to the VGA jack works. or not.? (we bypass screen this way local)
yes or now.
no, solderballs bad. or worse. (learn that worse can happen)
yes, works , then the PC is ok, is it not, just bad back lamps
as all do this old now. CCLF lamps dead
6: shine a flash light at the local LCD screen see data.
oops bad CCLF.


this page covers every possible way to get BLACK screens of *****.

http://pcdied.com/black-screen.html

Perform a Hard Reset Do these actions first to clear all temporary setting before troubleshooting the problem.Disconnect all peripheral devices and remove all USB devices and media cards.Disconnect the AC power adapter, remove the battery, and then press and hold the power button for at least 15 seconds to drain residual charge.Reconnect the AC power adapter (do not connect the battery), press the Power button and look for the LEDs to blink or glow, and listen for the sound of a disk drive and fan turning.Perform each recommended corrective action and then attempt to restart the computer.Symptom 1: LED lights do not glow, display is black, no fan or drive sounds are heard, and computer does not startIf LEDs do not glow or blink when AC power adapter is attached and power button is pressed, there is no power available to the notebook Check AC adapter wiring and power connection to the notebook Connect a different AC power adapter and remove battery, then restart notebook.Connect a different battery and disconnect AC power adapter, then restart notebook Symptom 2: LEDs blink or computer beeps but does not start Blinking LEDs or beep tones indicate a hardware failure during the pre-start up testing Count number of blinking LEDs or beeping tones to help with diagnostics testing Symptom 3: LEDs glow, fan noise may be heard briefly, display remains black, and computer fails to startup or boot Usually occurs if a component is installed incorrectly, or there is a device conflict or failure Connect an external monitor to check if the problem is the built-in LCD display or graphics card Remove all CD/DVDs, SD cards, USB devices, peripherals and do a Hard Reset If memory or hard drive components were replaced, reinstall original component Remove memory modules and replace one-at-a-time Remove and reseat hard drive If possible, turn on power, press F10 to enter BIOS mode, and run Memory Test and Hard Drive Test On newer notebooks, turn on power, press Esc to enter UEFI mode, and run Memory Test and Hard Drive Test If possible, turn on power, press F8 to enter Windows Advanced Boot Options , and select Repair Computer option, or enter Safe Mode and run Memory Diagnostics If all other methods fail , but computer can boot to BIOS, use recovery disk to recover the computer to original condition Symptom 4: Computer may display an error message on a black screen during startup or boot Search www.microsoft.com for terms in error message Search www.hp.com for terms in error message

If possible, turn on power, press F10 to enter BIOS mode, do the corrective actions listed under Symptom 3 to run memory and hard drive tests.

Symptom 5: Computer displays a blue screen or continually re-starts After an error message is displayed, you can usually bypass the error and continue to run the notebook in Safe mode to install an updated BIOS or driver.

• Search www.microsoft.com for terms in error message.
• Search www.hp.com for terms in error message.
• If possible, turn on power, press F10 to enter BIOS mode, and run diagnostic Memory test and Hard Drive test .
• If possible, turn on power, press F8 to enter Windows Advanced Boot Options , and do one or more of the following:
  • Select Disable automatic restart on system failure to view error message.
  • Run Repair Your Computer .
  • Run Last Known Good Configuration .
  • Select Boot into Safe Mode and then select Run a Microsoft system restore .
  • Select Boot into Safe Mode and then select Uninstall recently installed programs .
  • Select Boot into Safe Mode and then run Windows Update .

Symptom 6: Computer displays the Windows logo screen and stops responding If no error message displays, turn on power, press F8 to enter Windows Advanced boot options ,and select Disable auto-restart to view error message.

• Search www.microsoft.com for terms in error message.
• Search www.hp.com for terms in error message.
• If possible, turn on power, press F10 to enter BIOS mode, and select Restore the BIOS defaults (F9) .
• If possible, turn on power, press F10 to enter BIOS mode, and run Hard Drive Test .
• If possible, turn on power, press F8 to enter Windows Advanced Boot Options , and select Last Known Good Configuration (Advanced) . .
• If possible, turn on power, press F8 to enter Windows Advanced Boot Options , and select Boot into Safe Mode and then Uninstall recently installed programs .

Update Computer After Resolving A Problem When the computer starts into Windows normally, you should install the latest updates and patches to prevent other start-up problems.

step one, big battery out? skipped that?
step 2, a good power pack , that means 19vdc on those 2 pins.
bingo BIOS screen now work ,yes?
step 3, try an external VGA screen at the P15 VGA jack there
screens work now (BIOS first) yes/no?

remove DVD, drive
and all USB devices
there booting with only 1 memory stick. (got more?, try each 1 by 1)
black screens of *****'.

the lack of flash codes, Implies Power pack is dead. or CPU overheated, and selfshuts down. that fan going dead tells
me the power park is dead.

http://pcdied.com/#black-screens

seems like your motherboard has burn out, you should get new one.

Instructions

1. When you press the Power button to start the boot process, the LED lights glow while the computer verifies that there is sufficient electrical power to activate the hardware.
   
   Effect & Solution: When you press the power button, the LED lights on the computer do not glow or the LEDs blink briefly and then stop. There is no sound of the fan or hard drive spinning, and the screen remains blank. The computer will not start if there is insufficient battery or AC adapter power.
   
2. The BIOS queries various hardware components used for the startup boot process.
   
   Effect & Solution: When you press the power button, the LEDs glow but there is no fan or hard drive sound. The LEDs may glow briefly and then go out.
   
   Or
   
   The LED lights blink, stop, and then blink a second or third time, but there is no sound from the computer and the screen remains blank. The sequence of the blinking lights indicates a specific error code.
   
   Or
   
   A series of beeping tones is heard. The sequence of beeping tones indicate a specific error code.
   
   If a hardware component has recently been replaced, or if the PC has been jarred or shaken, there may be a loose connection to the memory chips or hard drive which prevents the computer from starting.
   
3. The BIOS loads the basic input (keyboard) and output (advanced LEDs / display screen / boot drives) devices into memory.
   
   Effect & Solution: When you press the power button, the LEDs glow, the fan or hard drive sounds, are heard, but then the boot process stops and a black screen - with an error message - displays.
   
   The boot check has detected a communication error or conflict with a hardware component that must be corrected.
   
4. The BIOS loads the Windows operating system and starts the services that allow low-level control of all of the background operations.
   
   Effect & Solution: When you press the power button, the LEDs glow, the fan or hard drive sounds, are heard, the HP or Compaq Logo displays on a black screen, but then the boot process stops and a blue screen - with an error message - displays.
   
   The boot check has detected a hardware driver error or a software conflict that must be corrected.
   
5. Control is transferred to the Windows loader to initiate the display of the advanced settings in the Windows environment.
   
   The Windows logo displays during this step.
   
   Effect & Solution: When you press the power button, the computer performs all the steps in the boot process, but after the Windows Logo displays, the moving Windows progress bar or the rotating cursor stops moving and the boot process stops.
   
   An error message may display on a screen with the Windows logo. In some instances, there is no specific error message.
   
   Or
   
   A black screen appears and the computer attempts to restart.
   
   The Windows self-check has detected a software conflict that must be corrected.
   

If a PC suddenly fails to boot properly, you should perform a hard reset as the first action. Performing the hard reset will correct many problems. If the computer still does not start properly, select your symptom from the list below to guide you to the recommended corrective actions.

1. Disconnect all peripheral devices and remove all USB devices and SD media cards. You want to test the computer not the accessories!
2. Disconnect the AC power adapter, remove the battery, and then press and hold the power button for at least 15 seconds to drain all residual power and restore default startup settings.
3. Reconnect the AC power adapter (but do not insert the battery), Press the Power button, Look for glowing LEDs near caps lock and num lock keys, and Listen for sounds of a fan or other moving parts turning.
4. If the computer does not start, the LED lights do not glow, and the display is black, you can perform one or more of the following actions to resolve the no power issue.
   • Verify the computer is receiving power from the AC adapter . Verify that the AC adapter is not damaged and is connected correctly to a working wall outlet plug. Verify AC power is connected to the system board by examining the AC adapter, wiring, and pin connection for damage. The keyboard LEDs will glow when AC power is connected to the system board. Damaged components, like the AC adapter or the pin in the power connector, may require an HP-certified repair.
   • Use a different AC power adapter . If you have access to a different AC adapter or power pack that is designed for the computer, connect it to the notebook and try to start the computer. If you own or have access to more than one notebook, verify that you are using the adapter which belongs to the notebook. CAUTION: Using a power adapter that does not meet the power requirements or has the wrong type of connector may damage the computer. On newer notebook models, connecting the wrong adapter to the notebook may cause the power LED lights to blink but not power the computer.
   • Remove the battery and boot on AC power only . A discharged or defective battery may prevent the AC adapter from supplying enough power to start the computer. To verify that power from the AC adapter is available for PC; remove the battery, connect AC power adapter, and press power button. If available, try using a different AC adapter, that is rated for the PC, and repeat this test.
     • If LEDS do not glow and the fan or hard drive do not spin, AC adapter may need to be replaced.
     • If LEDs glow and PC boots, the battery may need to be replaced.
     • If LEDs glow but PC does not boot, go to LEDs glow, fan is heard, but display is black or blank section.
   • Remove the AC adapter and boot on battery power only . A defective AC adapter may not charge the battery and prevent the computer from booting on battery power only. To verify battery power available for the PC; connect AC power adapter, allow battery to charge for 30 minutes or more, disconnect the power adapter and press power button. If available, try using a fully charged battery, of the same type, from another computer and repeat this test.
     • If LEDS do not glow and the fan or hard drive do not spin, battery may need to be replaced.
     • If tests of both the battery and the AC adapter fail, there may be a problem with system board requiring service by HP.
     • If LEDs glow and PC boots, the AC adapter may need to be replaced.
     • If LEDs glow, but PC does not boot go to LEDs glow, fan is heard, but display is black or blank section.

Now when you say blue power light, what are the rest of the lights doing, does the hard drive light flash, does the fans turn on, does the hard drive make it's spinning noise, if so you may just have a bad LCD inverter which is very common and about a 40$ part. you can test this by trying to hook the laptop up to an external monitor and see what happens.