Re: Another solution...
"...remove the battery."
The problem with that is the some laptops (I've had at least two) route mains power through the battery - so if the battery isn't there physically then the power adaptor does zip and the laptop remains dead.
I've also had one machine (a Dell Latitude) that objected vehemently to me removing the battery (it failed) where the machine POST'd fine, but then gave me a BIOS error screen claiming that the battery 'had failed or was not present' with the sole option being pressing a key to shutdown.
So, it's a nice idea to remove the battery when on mains, but isn't practical in all circumstances. Furthermore from watching the power light on my Dell D620 it would appear that this 'trickle charges' the battery when full. Checking the battery meter app on Ubuntu seems to bear this out.
I'm still kind of confused as to why the _laptop_ caught fire, usually if they overheat they just shutdown. In which case my money would be on the cause being a battery short or something amiss with the surface that it was resting on.
Any fire safety engineers out there in the Reg Land care to comment?