Power failure My laptop will not power up The screen is either black or sometimes it will say windows cannot load power supply problem and the screen and disk drive will shut down but the power button stays lit If I try to restart the screen will not even display a thing

You might like to Power it off completely by removing the Battery for a few seconds.
If that doesn't help, try booting from your Win7 Installation Disk.

use the softare diagnostic coming with the computer or get support via ONLINE chat.
However you must restart the computer HOLD the keys CTRL+f2 or f11 or f12 depend of your model, and go to restore to the factory defaulty.
God bless you

You may have a bad backlight screen power supply board and that is usually mounted in the bottom part of the screen right behind the front bezel. This supply's high voltage to the backlight tube that lights the screen. This is kind of like a small florescent tube that uses high voltage to fire the backlight and is a common failure point in laptop screens. Easy to fix, just pop the front bezel off and the module will be in the center bottom section of the screen. Do a YouTube search on how to disassemble your model's screen and the parts can be found on Ebay. Good luck.

yes,this is the battery
needs replacement or the power supply unit has lost it's ability to charge the battery.

If you're lucky, it can only be a software problem. Try to break the cycle by pressing F8 right after the HP logo. This should start your laptop in Safe Mode with Networking. Then, you'll need to see what's causing the problem. If you installed a new program or update just before this repeated shutdowns started, then you'll need to uninstall this program, or revert to the previous state of your computer using the Restore option (In Control panel-System). While you're in safe mode follow these great instructions for setting up PC security and check your system for viruses and malware. Sometimes they may cause unpredictable problems and random shutdowns could be one of them.
If you're not so lucky, you may be facing a power adapter failure, or a motherboard failure.
To test the power supply, run the laptop on battery only and see if it boots up OK. If the laptop's OK on battery alone then you'll need a new power supply. Go for a new one, specifically made for your laptop model, substitutes may not be within the accepted tolerance and you may end up having two useless adapters. Play it safe, get a matching/original brick.
If the laptop keeps restarting with or without the power supply, and you can't even get it to go into Safe Mode you may be looking at a motherboard problem. The most common power-related failure of the motherboard is the Maxim 1987 power regulator failure (learn how to repair this) . Another option would be a FSB chip failure which is also relatively easy to repair. Lastly, it could be a graphic chip failure, which can be repaired the same way as the FSB chip.
For a more precise diagnosis provide some more details of the messages you see on the screen, how far it gets to load Windows (if at all), can you see any LED blinks, sounds you hear etc. The more descriptive and detailed you are, the easier it is to get to an accurate diagnosis.

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Base from the description of your problem , this seems to be a motherboard failure already. The blacking out of your screen before this problem started is a sign of something on the motherboard is already failing.

Now since the computer will just power ON and automatically shut itself down is definitely an implication of motherboard and processor failure it can be due to overheating problem, so if you want to continue using this laptop a motherboard replacement is needed, you can take replace it by yourself if you have any experience doing those kind of things but if not better take it to a repair shop or better yet do a upgrade and get a new laptop then.

Try it on another PC nad also check the VGA cable and all the pins first.

Most common failures in the LCD monitors are bad capacitors (bulging top/seal or leaking) in the power supply, failed inverter circuits (blown fuse, shorted transistors, shorted/open transformers), bad lamps (poor solder connections or worn out lamps). You will need to open it up and inspect the inside, see example of failed ACER monitors to get some ideas what to look for: http://s807.photobucket.com/home/budm/allalbums
Post back what you see inside so we can guide you further and it will help out other people in the future also.
http://en.wikipedia.org/wiki/Capacitor_plague

http://www.badcaps.net

sir
markit me hi hoga kyonki laptop ki hdd me pro hai ja fir window sport nahi kar raha hai

are you connecting your laptop to a projector? check you windows settings. Sometimes this happens to some laptop when they're idle. when i encounter that, what i do is to close then open the lid of my laptop

I would try the following:
1. Remove the battery completely. If the computer boots properly several times in a row, then the battery may be causing the power supply to do strange things.
2. If you have experience removing laptop components, try removing the hard drive. Because you say the screen goes black (I assume the system powers off) sometimes after the HP logo, I doubt its Windows or a software issue.
3. If HP has a diagnostic CD you can boot to, try that.
4. It may be the power supply acting up. If it charges the battery, and if you can boot to Windows with the battery, try getting a new power supply.
5. Otherwise, it may be the motherboard of the laptop.