Sony Vaio VGN-NW20EF Laptop going dead !

[pchealthpoint]

I have a clients sony vaio VGN laptop that keeps going dead, i have used the laptop in safe mode while i did the usually de-clutter and virus scan and found no major issues, ccleaner worked a treat as i always usually find, but i have run into the other problem that the customer was having aswell as the computer seeming slow, every so often the laptop can go completely black screened give no warning, then shutdown and boot back up but sometimes you have to manually have to press the power button, i have tested the battery by unplugging the charger and just trying the on button to turn the laptop without being plugged in and this works fine so im under the conclusion that the battery seems ok, no blocked vents and good cooling all round the laptop.


any ideas

Thanks
Dan