I have a Sony Vaio VGN FS640 which I have had for quite a while now. The problem I noticed a while back is that the laptop would randomly switch off. (I don't have any virus or anything) It used to switch off on a hardware level, usually when i moved the laptop. This used to be a rather infrequent occurrence, but within the last week or so it happens almost one a day. I did a little research online and it seems to be a common problem with sony laptops caused by them overheating and shutting down. This I belive was the problem with my laptop because it used to get very hot at the bottom. Anyway I just let the laptop cool down for a min and then could start it up again.

Today however the laptop switched off and will not turn on even after i let it cool down for a couple of hrs. The AC adapter has a green light and I used a multimeter to check if it was working. everything ok there. But the laptop is completly dead, not even the charging light comes on.

I am pretty handy with a opening stuff up and fixing it, so I would like to try and fix the problem myself. (I can't really afford to send it in to store) or atleast be aware of what the real problem is so i can not get stiffed if i have to take it in. So I would really appreciate it if anyone here is fimilar with the problem and could give me any advise.

Thank you

definitely overheating, buy a chill pad for your notebook, and remember not to use the notebook on your lap, but on a hard, flat surface only. Make sure that the fans are not clogged with dust. If they are, use a can of compressed air to clean them out.

It exactly happened with my Sony Vaio FS640. I searched for solutions online and these were some of the advises:
1) Remove power supply connector and battery from laptop. Keep pressing Power button for 20-30 sec...i don't know exact time..but longer will be better. It will allow to discharge capacitors and it might work. Did not worked for me
2) Remove battery. Try switching it on only power supply connection.
If it does not work, try other way round. Remove power supply and switch on only on battery
did not worked for me
3) Remove both RAM and put it back, try switching ON. Put one RAM at a time and try. did not worked for me

I tried these things for few days and gave up. I kept my laptop in closet for 2-3 months thinking its gone. But to my surprise, after 3 month I was about to dump it, i gave it a last shot and pushed power supply button and holla its ON. Now running smoothly!

It had 2 problems after 3 months:
1) Its CMOS battery was down. Showing incorrect date time all the time. It was not keeping track of time after hibernating/switching off laptop. (CMOS: http://www.zkarlo.com/selected-zkarlo-part/laptop-battery-p2842.php)
2) it was heating and slowing down.

what i did:
I purchased CMOS battery and processor/chip/IC heatsink coumpund (white glue like fluid applied between processor and heatsink)
I opened the laptop and cleaned thoroughly the processor fan (which was very dusty) and used new heatsink coumpound for processor. Changed CMOS battery (remember: it is on BACK side of motherboard, blue/green battery color).

Now its worked fine.