There was something wrong with the power input to this laptop. Of course the connector was buried in a corner that required a near complete strip down. Connector sorted, and reassemble it for testing. Everything was eventually back in the correct place, with nothing left over. Alas the fault was still there, and must be on the main circuit board, which wouldn't be worth replacing.

Oh well a few hours wasted. I'd cleaned the whole thing out too, whilst it was apart. The owner's obviously a smoker, judging by the pong and sticky brown dust within. At least their data can be retrieved, as the hard disk was okay.