I'm trying to run Ubuntu on my Toshiba A200 computer and after a few minutes it's getting crashed and the computer restarts. I notice that the computer is overheating.
Does someone know this problem and can advise?
If that laptop is overheating, it is because the cooling channel has not been cleaned out recently... if ever. Also, the design is such (the way it utilizes an earlier design to have the heat sink at the end of a heat pipe to shunt the heat generated by the processor completely off the motherboard) that if the heat pipe is bent *AT ALL IN ANY WAY more than the original specs allow, the heat sink itself will be pushed by the casing upon re-assembly, which will translate to the copper pad on the processor being levered slightly OFF the processor, making the transfer of heat less efficient.
Believe me on this. I spent days on an A215 trying to figure out why it would overheat ONLY when assembled, but would run fine when taken apart... took me a bit to catch that. So, if the unit has ever been taken apart to have the cooling channel cleaned (the blanket of dust that gathers between the fan and the heat sink) it is entirely possible that the heat pipe between the copper processor pad and the heat sink was bent when it was put back together. That is IF it was ever cleaned.
If it has never been cleaned, then the unit needs to be taken apart, the fan removed, and the blanket of dust taken out of there. You see... a little dust gathers on the leading edge of the heat sink fins, and that little dust catches more dust... and pretty soon (6 months to a year) you have a layer looking like it came out of a clothes dryer lint trap.
Now, that Model Toshiba also came with software to allow you to underclock the processor to save battery power (they've been doing that with their custom power management software since before the A70 series). It doesn't quite run as efficiently as Cool & Quiet. It's not the kind of thing that automatically underclocks until you need more power. It's a blunt setting kind of deal.
So... clean the laptop. Clean it well. Or... get it cleaned.
EDIT The reasons why you see a difference with Windows 7... it could be due to the fact that the power management within Windows 7 does a better job at controlling the fan speed. It could be due to the fact that it will underclock the processor to extend battery life and reduce heat generation.
However, none of that changes the fact that EVERY laptop will suck dust and debris up it's cooling fan, and blow it against the heat sink... until there is a layer of material there that will impede air flow and cause overheating. That's a 5+ year old laptop, using a single fan/90 degree cooling assembly. Look at this image...
That's a heat sink from a C655... and that's only after a year and a half. If you have no idea when yours was cleaned last, don't obfuscate the issue with how "well" it runs with Windows 7. Get it cleaned, and imagine how well it will run with ANY OS.