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Today, when arrived at home and started my Windows XP computer, I found the screen was black during start up. It said no computer input. (I am posting this question with my mobile.) Please help!

The display card is a Sapphire HD4850. There is no red light on the display card, I've clean the dust, and the fans are spinning, so there should not be an overheat problem.

The CPU is okay because I see the fan on it is spinning.

The PSU is normal -- no problem.

By the way, does the motherboard provide an onboard display usually? I found there is another port to plug with my monitor cable, and i tried to use that, but I still get a black screen during start up and onwards. Any clues?

Edit: when i said black screen, it means the monitor is idle waiting for input, saying no input from computer. So black screen, i suppose the windows is okay booting up…just assume.

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up vote 1 down vote accepted

Try a deep power cycle, which will hopefully resolve this problem for you (it has for some of my clients who've encountered it on rare occasions):

  1. Shut down the computer and power it off
  2. Disconnect the power cable
  3. Attempt to power on the computer using the power switch (it won't power on)
  4. Re-connect the power cable
  5. Attempt to power on the computer using the power switch (it should power on)

If this doesn't resolve the issue, then you probably have a malfunctioning power supply (testing equipment doesn't always tell us everything) or motherboard (hopefully it's only the power supply as this is a lot less expensive to replace).

Also, most motherboards do provide a display immediately after powering up, but some do present a bit of a delay first (especially certain models of server motherboards which can delay for up to 5 minutes before activating the display -- these motherboards are particularly annoying when you're dealing with a server problem, and even stressful, even though the vendors continue to insist on doing this by design).

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When I pull out the computer to check it, I already disconnected the cable. Of course I plugged it back too, and it won show any display. – lamwaiman1988 Jul 5 '11 at 1:05
Please read my instructions, especially point number 3 as it is significant (and depends on point number 2). – Randolf Richardson Jul 5 '11 at 5:40
Okay...I will try it when I back home. – lamwaiman1988 Jul 5 '11 at 5:57
This is godly! My display is back! Why did it work? What's the problem??? – lamwaiman1988 Jul 5 '11 at 13:04
Some of the capacitors (most likely) in your system may have been overcharged, and this deep power cycle I suggested resets it all to nothing (as if new). With the correct power levels, all those little complex circuits on your motherboard function correctly and with correct timing, yet when the wrong power levels are present then unpredictable things may occur (with the end result simply being "no video" or, more commonly, odd symptoms that are nearly impossible to troubleshoot). I wonder how many good motherboards have been replaced (globally) because this technique wasn't attempted. – Randolf Richardson Jul 5 '11 at 20:45

In order to user the on-board graphics you will most likely need to remove the graphics card.

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