Same thing has happened to my laptop twice, which is also a megabook s430. First time, I left the computer on the past night for some reason and then the next morning when I tried to start the computer up, it was unresponsive, it would sometimes boot with the fans and lights etc, but no screen response. I decided to replace the laptop cpu, which was a semperon originally, which after it crashed and burned, decided to load a turion inside. After that, started the laptop, and it booted perfectly. Recently I left the computer on again for updates on sp1 etc for about 5hrs straight. same thing happened, burned out again. and is still experiencing the same symptoms as before. My guess is that this laptop has a shoddy cooling system loaded in it, causing the laptop to continuosly die on us when using it for an extensive perios of time for things like gaming etc. My advice is that you dont bother with this laptop anymore, unless you wish to give it one last chance. cpu's can be bought cheap off of ebay for under $50, but if you do this, make sure to apply thermal paste.
Hope this helps