Internal power unit 'short'.

probably ur battery is dead or your loading circuit is malfunctioning, due to internal circuitry overload most like to overheating.

Most sony laptop power supplies have a power LED that indicates if the device is A) plugged in {ok it happens!}, or B) fried and not providing power to the laptop. Check this first. If the power supply is plugged in and the LED is on (usually green or red) then see if you have ANY lights on the laptop itself. Its possible that your LCD display went bad but that the laptop is otherwise running. You may see a power, hard drive or wireless network light on if the laptop works but the LCD went bad. You can also connect an external monitor to the laptop and power it up to check the LCD.
I've also seen where the battery goes bad and it keeps the laptop from booting. Try removing the battery and power up (with the ac adapter plugged in) again.
If neither of these helps, you may be looking at some kind of internal short on the motherboard which is big money. Hopefully that isn't the case.
Hope this helps!!

Can you describe the symbols that are next to the lights that are still lit?
If your laptop is still attached to mains power (ie your power pack that feeds DC voltage to your laptop) the battery pack may be still charging (indicated by a light) The battery pack is internal to your laptop and this powers your laptop when the power pack is not connected to mains.
Try disconnecting your mains power and see if a light goes off. If it does then that light is the light which indicates charging is in progress.
Other lights that are typical to laptops are:
a. hard drive activity (usually lights when the hard drive is being used) Usually has an adjacent symbol which looks like a metal can or cylinder.
b. bluetooth (wireless connection to other bluetooth devices such as cell phones, other bluetooth devices such as another computer) Adjacent symbol looks like two triangles side by side.
c. sleep (usually lit when your laptop goes to sleep and saving power) This may be covered by the power on lamp mentioned below, and the power light may flash to indicate the laptop is in sleep mode to save battery power.
d. power on (lights when your laptop is ON)
e. battery charging (as described above). There is often a symbol adjacent to this light that looks like a small battery.
Good luck,
Steve (Melb, Australia)

If the power LED is lit before connecting to your laptop and then goes out as soon as you connect to your laptop, then you either have a short circuit in the power supply module of your laptop, or you battery is causing the fault.

Remove the battery and try again. If it powers up the battery needs replacing. If the problem is still the same then you need someone to look at the power supply module in the laptop

Take the battery out and try to boot the computer up with the external power supply.. If this works the the battery is shorted. If it doesn't then you will need to try another power supply, if that doesn't work then something internal has shorted in laptop

Laptop is dead. How to troubleshoot the problem.
In this post I’ll explain how to troubleshoot a dead laptop and find the problem. The following troubleshooting tips are not model and brand specific, they should work for most laptops.
Let’s take a look at two different scenarios.
Example 1. The laptop is absolutely dead.
When you plug in the power adapter and press on the power button, there is no signs of life at all. The laptop will not make usual noises, LEDs will not light up, the fan will not spin, the screen is blank and black, etc… In short, the laptop is dead.
What you can do in this case?
1. Make sure the wall outlet is working and the laptop DC adapter is getting power from the outlet. Try another wall outlet.
2. Test the laptop DC power adapter, make sure the voltage output is correct. You can test the DC power adapter with a voltmeter.
3. Let’s say the DC adapter is fine and the adapter outputs correct voltage. In this case unplug the power adapter from the laptop, remove the battery, wait for 1-2 minutes, plug in the adapter and try turning on the laptop again.
OK, you tested the adapter and it’s bad. If you decide to replace the original DC adapter with a generic one, you’ll have to follow this rule:
The voltage output on your new adapter has to be exactly the same as on the original adapter. The amperage on the new adapter could be the same or higher.
If nothing helps and the laptop is still dead, apparently the motherboard is fried or there is a problem with the DC power jack. It’s possible the DC power jack is broken and the motherboard is not getting any power from the adapter. In this case you’ll have to disassemble the laptop and replace the power jack.
Example 2. When you plug the DC power adapter and press on the power button, the laptop starts making normal noises, the LEDs work properly but noting appears on the screen. The laptop will not start.
First of all, take a closer look at the LCD screen. Look at the screen under bright light. It’s possible that the image is still on the screen but it’s very faint.
If there is no image on the laptop LCD screen, test the laptop with an external monitor. Connect an external monitor to the VGA port on your laptop and turn the laptop on. You can toggle video output between the internal LCD screen and external monitor by pressing Fn and F4 keys simultaneously on HP laptops, Fn and F5 keys on Toshiba laptops, Fn and F7 keys on IBM laptops. Other laptops may use different key combinations.
Let’s say the external monitor works fine but the internal LCD screen has no image at all. If that’s the case, your problem could be related to the LCD screen or the video cable. Also, make sure the video cable makes good connection with the motherboard and the LCD screen. Try reconnecting, reseating the cable.
In my case, both internal and external monitors were absolutely dead. Neither of them had image. That means the problem is not related to the LCD screen or the video cable. From my experience I know that this problem could be related to the laptop memory.
Try reseating the memory module, maybe it’s not making good connection with the memory slot. Try cleaning contacts on the memory module with pen eraser. Try moving the memory module into another slot. Try replacing the memory module with another known good module, it’s possible that your original module is dead.
If you have two memory modules installed you can try removing them one by one, it’s possible that one of the modules is bad. Try installing different memory modules into different memory slots.
In my case reseating, swapping the memory module didn’t help. I was pretty confident that my problem is not memory related and I moved on.
Try removing battery, hard drive and DVD drive and turning on the laptop without these components.
Also, try turning on the laptop with an external monitor when the video cable is unplugged from the motherboard. If the laptop start with video on the external monitor, apparently there is something wrong with the laptop display panel.
Finally, disassemble the laptop and removed the motherboard.
1. Motherboard. Like on most laptops, in my case the video card is integrated into the motherboard
2. CPU with heatsink and cooling fan.
3. Known good memory module.
4. The power button board witch you need to turn on the system.
5. Working DC power adapter.
Still cannot get any video on the external monitor. The system turns on, the cooling fan starts spinning but there is no video.
At this point I’m 95% sure that the motherboard is dead. CPU failures are not very common, so it must be bad motherboard.

If the light on the A/C adapter "goes out" when you connect it to the Laptop... then your motherboard is bad.

Your motherboard is "shorting out" the A/C adapter, in which case you will need a new motherboard.

Sorry....

dear lis,
looks like the battery pack is low, you may think about getting a newer one or using it simply as astationary pc now.

thats what i suggested earlier, the AC adapter in the laptop has blown, thats what causing the feedback/overload. you can fix the problem yourself but it is a big job!!!
If you need the problem resolving straight away, then take it to be repaired, under warranty if its still covered by it!!
Sorry for the misunderstanding

Kind regards

The fact that the LED light on the power supply tells me that its receiving power, look where the AC adapter goes and check the pin to see if it is loose, this sounds like feedback from the computer causing the power supply light to dim or go out

let me know how you get on