My Sony Vaio - VGN AW4 - was working fine until yesterday, I tried to shut it down as usual but the power button LED stayed on and i couldn't turn the laptop off by holding the power button in for several seconds. Finally took the battery out, and tried again, power LED comes on, fans work, but windows doesn't boot. Nothing. I tried about 2 dozen times then once, by chance, windows booted up. Since then, same problem, never boots, and power button will not shut down laptop. Any ideas please?